History of International Law

Introduction

The history of International Law is not a linear account of civilised progress. It is the record of how political authority, commercial power, war, empire, religion, statehood, anti-colonial resistance, and institutional design were translated into legal arguments. At each major turning point, the discipline redefined at least one basic question: who counts as a legal subject, what creates legal obligation, which forms of violence are lawful, how territory may be claimed, and how law can restrain power while also serving it.

This article treats international law as a historical field shaped by conflict and argument, not as a finished system that simply expanded over time. Ancient treaties, Roman ius gentium, medieval just-war doctrine, scholastic natural law, maritime commerce, Westphalian sovereignty, nineteenth-century positivism, the League of Nations, the United Nations Charter, decolonisation, human rights, international criminal law, and environmental governance all belong to the story. Yet they do not belong to it in the same way. Some provided vocabulary. Some built institutions. Some justified domination. Others created tools of resistance.

A serious account cannot begin with the claim that international law was born fully formed in Europe. That version is too narrow. It ignores ancient diplomatic practice, Islamic legal thought, Latin American doctrine, anti-colonial claims, Indigenous legal struggles, and Third World legal agency. At the same time, it would be equally misleading to describe every ancient rule of diplomacy or warfare as modern international law. The better method is to ask what each period contributed to the legal architecture that later became recognisable as international law.

This distinction matters because international legal history is often used to legitimise present doctrine. Lawyers have long relied on origin stories to give authority to concepts such as sovereignty, consent, territorial title, treaty obligation, and the prohibition of force. Historians tend to be more cautious: they ask what those concepts meant in their own political, economic, and intellectual settings. Vadi argues that this tension between “jurists’ history” and “historians’ history” is one of the central methodological problems of the field (Vadi, 2017). A strong article must use both approaches without confusing them.

The history of International Law also requires direct engagement with Eurocentrism. Classic accounts often made Europe the silent standard of legal development, while non-European societies appeared mainly as objects of conquest, trade, recognition, or reform. Koskenniemi’s critique remains important because it shows how even critical histories can continue to rely on European categories of progress, civilisation, and modernity (Koskenniemi, 2011). A credible account must examine Europe’s central role without treating European experience as universal experience.

The colonial encounter is one of the clearest examples. The legal debates surrounding Iberian expansion, the Treaty of Tordesillas, the School of Salamanca, Grotius, and maritime freedom were not abstract exercises in legal philosophy. They were tied to conquest, trade, conversion, navigation, territorial title, and the status of non-European peoples. Anghie’s work is crucial here because it shows that sovereignty did not merely regulate relations between equal European states; it also helped organise unequal relations between Europe and the wider world (Anghie, 2005).

The same double character appears in later periods. Nineteenth-century international law professionalised diplomacy, arbitration, and humanitarian restraint, but it also developed the standard of civilisation, unequal treaties, protectorates, and legal techniques of empire. The UN Charter later placed sovereign equality, peaceful settlement, human rights, and the prohibition of force at the centre of the legal order, yet great-power privilege remained embedded in the Security Council. Klabbers is right to caution that international law is neither inherently virtuous nor inherently malign; it is a framework that can be used for very different political projects (Klabbers, 2024).

This article argues that the discipline’s history is best understood through changes in legal authority: who makes law, who is bound by law, who benefits from law, and who can challenge law. The key issue is not only what happened, but what changed legally after it happened. The rise of the state changed legal personality. The law of the sea changed jurisdiction and commerce. Positivism changed the role of consent. Decolonisation changed membership and self-determination. Human rights changed the boundary between domestic jurisdiction and international concern. International criminal law changed the legal position of individuals. Environmental law changed the temporal horizon of legal responsibility.

This approach gives the history of International Law practical value for advanced readers. It explains why sovereignty remains both a shield and a claim to authority, why treaty law depends on consent but cannot be reduced to consent alone, why self-determination still unsettles territorial order, why human rights challenge domestic exclusivity, and why global problems such as climate change, cyber operations, and corporate power strain older legal categories. The past does not provide easy answers, but it exposes the assumptions built into the doctrines still used today.

1. How to Read International Legal History

The history of international law cannot be written as a search for one clean beginning. That method produces attractive stories, but weak analysis. It makes the field look as if it moved neatly from ancient diplomacy to Roman law, then to Grotius, Westphalia, positivism, the United Nations, and contemporary global governance. The real history is less tidy. Different periods produced different legal techniques, and later lawyers often reorganised those materials into a discipline that looked more coherent than it had been.

A stronger method asks a narrower question: when did particular rules, concepts, and institutions become legally useful across political communities? This avoids two mistakes. The first is to claim that modern international law already existed in ancient treaties, religious texts, or imperial practice. The second is to claim that international law was born only in seventeenth-century Europe. Both positions flatten the subject. Ancient treaties, Roman ius gentium, medieval just-war doctrine, Salamanca, Grotius, Westphalia, and the UN Charter are not parts of one continuous legal system. They are layers of legal thought, practice, and institutional memory, later used to construct the field.

1.1 Origins, myths, and legal function

Origin stories have always had power in international law. They give legal doctrines a sense of age, dignity, and authority. The Peace of Westphalia is the best-known example. It is often treated as the moment when modern international law began, because it is associated with state sovereignty, territorial authority, and non-intervention. That story remains influential, but it is too simple. Westphalia did not create modern sovereignty in one legal act, nor did it establish a universal order of equal states. Its importance lies partly in what happened in 1648, and partly in how later lawyers used Westphalia as a symbol of modern statehood (Koskenniemi, 2011).

The same problem appears with Grotius. He is often called the father of international law, but that title hides more than it explains. Grotius wrote in a world of maritime rivalry, imperial expansion, commercial violence, and Dutch competition with Iberian powers. His work matters because it systematises arguments about war, peace, trade, and the sea. It should not be treated as the private invention of a neutral legal science. The legal history of Grotius is also a history of commerce, naval force, corporate power, and colonial encounter (Anghie, 2005; van Ittersum, 2006).

Legal function is a better guide than legal mythology. A rule matters historically when it performs a recognisable legal task: allocating authority, defining status, regulating violence, legitimising territory, protecting envoys, structuring trade, creating responsibility, or limiting the use of force. The Kadesh Treaty, for example, matters not because it was modern treaty law, but because it shows that political communities used formal agreements to settle conflict, create alliances, and regulate return obligations long before the modern state system (Langdon and Gardiner, 1920).

1.2 Historians and jurists

International legal history sits between two disciplines that do not ask the same questions. Historians usually want to understand the past within its own setting. They ask what actors believed, what institutions existed, what economic pressures operated, and what political choices were available. Jurists often approach the past differently. They look for the genealogy of current doctrines, such as sovereignty, consent, recognition, treaty interpretation, self-determination, and human rights.

Both methods are useful, but each has risks. A purely historical approach may describe context with great care, while failing to explain why a legal doctrine still matters. A purely legal approach may find the present everywhere in the past, even where the earlier legal world operated through different assumptions. Vadi describes this as the tension between “historians’ history” and “jurists’ history”, a methodological problem that has shaped the field of international legal history (Vadi, 2017).

This article uses both approaches. It reads ancient treaties, medieval just-war theory, scholastic natural law, early modern maritime doctrine, nineteenth-century positivism, and the UN Charter in their own contexts. It also asks how later doctrines developed through those materials. That combination is necessary because international law is both a legal discipline and a historical practice. It is made through treaties, customs, institutions, judicial reasoning, diplomatic language, scholarly argument, and political struggle.

1.3 Eurocentrism and selection

Classical histories often made Europe the centre of international law’s development. Non-European peoples appeared mainly as conquered populations, trading partners, mandate territories, colonial subjects, or states waiting to be admitted into a European legal order. That structure is not just incomplete. It distorts the subject.

A serious account must include Europe, because European expansion deeply shaped modern international law. Yet Europe cannot be treated as the whole story. Ancient Near Eastern treaty practice, Indian legal thought, Islamic rules on warfare, Chinese diplomatic traditions, Latin American doctrines of non-intervention, Afro-Asian anti-colonial claims, Indigenous legal struggles, and Third World approaches all belong to the history of international law. They show that legal order was not made by Europe alone, even when European powers tried to define the terms of legal membership.

Eurocentrism also affects the choice of turning points. If the story begins with Grotius and Westphalia, colonialism can look like a later distortion of an otherwise European law of equality. That is misleading. Colonial encounter was not peripheral. It shaped debates on sovereignty, territory, trade, legal personality, civilisation, intervention, and jurisdiction. The Spanish encounter with Indigenous peoples, the Portuguese and Dutch contests over maritime commerce, the Berlin Conference, and the mandate system all show that international law developed through hierarchy as well as equality (Anghie, 2005; Koskenniemi, 2011).

1.4 Turning points, not a timeline

This article follows turning points, not a mechanical chronology. A turning point matters when it changes the structure of legal authority. Some turning points changed who could make laws. Others changed who could be bound by law, who could claim rights, who could own territory, who could use force, who could appear before institutions, or who could challenge domination.

This method gives the article a doctrinal spine. The rise of the sovereign state changed legal personality. Maritime law changed the relationship between trade, jurisdiction, and ocean space. Nineteenth-century positivism changed the role of consent and recognition. The Hague and League periods changed expectations about arbitration, adjudication, and collective order. The UN Charter changed the law on force. Decolonisation changed the legal meaning of self-determination. Human rights changed the boundary between domestic jurisdiction and international concern. International criminal law changed the position of individuals. Environmental law changed the temporal scale of responsibility.

A timeline can show a sequence. It cannot, by itself, explain legal transformation. The central issue is what changed in the legal imagination after each event, doctrine, or institution entered the field.

2. Ancient Inter-Polity Practice

Ancient political communities did not have modern international law. They did not operate through a universal system of sovereign equality, treaty registration, permanent international courts, codified diplomatic law, or a general prohibition on force. Yet they did develop practices that later international lawyers could recognise as legally significant: treaties, envoys, truces, alliances, maritime customs, rules about captives, and restraints on certain forms of violence.

The value of ancient practice lies in comparison, not direct continuity. It shows that political communities needed rules before the modern state existed. They needed ways to end war, exchange messages, protect representatives, organise trade, settle disputes, and distinguish lawful conduct from betrayal. These needs were not modern. What changed over time was the legal vocabulary used to organise them.

2.1 Treaties before sovereign states

The Kadesh Treaty, concluded between Egypt and the Hittite Empire in the thirteenth century BCE, is one of the most important examples of ancient treaty practice. It followed a conflict between two major powers, and it contained provisions on peace, alliance, mutual assistance, and the return of fugitives. Its significance is not that it created treaty law in the modern sense. Its significance is that it shows how formal agreement could transform military rivalry into a structured legal and political relationship (Langdon and Gardiner, 1920).

The treaty also shows why ancient law cannot be read through modern categories without caution. The parties were empires ruled by monarchs, not sovereign states acting through constitutional systems of external representation. The treaty’s authority rested on royal power, religious sanction, dynastic legitimacy, and political necessity. It was not based on sovereign equality as understood after the rise of the modern state.

Even so, the legal function is clear. The Kadesh Treaty helped stabilise relations, reduce conflict, define obligations, and create expectations about future conduct. Those are recognisable treaty functions. Later international law would develop different rules about consent, interpretation, invalidity, succession, registration, and third states. The basic need, however, was already visible: political communities used formal commitments because force alone could not manage long-term relations.

2.2 Envoys and diplomatic protection

Diplomatic protection also has ancient roots. Political communities needed envoys because rulers could not negotiate, warn, trade, form alliances, or end hostilities without communication. An envoy who could be attacked at will was useless. For that reason, many ancient societies developed rules, customs, or religious restraints protecting messengers and representatives.

Ancient China provides important examples of travelling envoys and diplomatic missions between political communities. Ancient India, Mesopotamia, Greece, and Rome also developed practices involving messengers, heralds, ambassadors, and protected representatives. These arrangements were not identical, and they did not form a single law of diplomatic relations. They did, however, show a shared practical logic: communication between political authorities required personal security.

Modern diplomatic law rests on different foundations. The Vienna Convention on Diplomatic Relations codifies inviolability, immunity, mission premises, diplomatic communication, privileges, duties, and persona non grata. Ancient rules did not contain that structure. Their relevance lies in function. They show why diplomatic immunity later became a core institution of international law: legal relations between political communities depend on protected channels of communication.

2.3 Maritime practice and trade customs

Trade created another early need for shared rules. Maritime commerce exposed merchants, rulers, and shipowners to recurring problems: cargo loss, piracy, shipwreck, passage, port access, jurisdiction, and liability. Ancient Mediterranean practice, especially the Rhodian maritime custom, became important because sea trade required rules that could travel across political boundaries.

The sea was never only a physical space. It was a legal problem. Who controlled passage? Which authority governed a ship? What happened when cargo was sacrificed to save a vessel? How should coastal power be balanced against navigation and trade? These questions did not wait for modern international law. They appeared wherever maritime commerce became regular enough to require predictable norms.

This ancient maritime background prepares the reader for later disputes about mare liberum, territorial seas, naval power, piracy, prize law, exclusive economic zones, and the common heritage of mankind. The doctrinal vocabulary changed across centuries, but the underlying tension remained: the sea could be treated as a route of shared use, a zone of imperial control, a theatre of war, or a field of commercial freedom.

2.4 Early limits on violence

Ancient and pre-modern restraints on violence are essential to a serious history of international law. The modern law of armed conflict did not appear fully formed in the nineteenth or twentieth century. Earlier legal, religious, and ethical traditions had already addressed the treatment of civilians, captives, envoys, the wounded, and non-combatants.

Ancient Indian texts, including the Laws of Manu, contain rules on statecraft and warfare, including ideas connected with proportionality, protection of certain persons, and limits on destructive methods. Islamic legal traditions also developed important rules on the conduct of war, including protection for women, children, the elderly, religious persons, crops, trees, and captives. The reported instructions associated with Abu Bakr are often cited as an early example of restraints on military conduct in Islamic tradition (Aboul-Enein and Zuhur, 2004).

These examples matter because they challenge a narrow Western genealogy of humanitarian restraint. Rules about civilians, captives, treachery, and unnecessary destruction were not exclusively European inventions. Yet precision is necessary. These were not the Geneva Conventions, and they did not create the modern distinction between jus ad bellum and jus in bello. Their importance lies in showing that many legal cultures tried to separate legitimate violence from excess, cruelty, treachery, and destruction without military necessity.

The main lesson is historical and doctrinal. Ancient inter-polity practice did not produce modern international law, but it produced legal functions that remained central: agreement, representation, trade, restraint, and obligation. Later international law would reorganise those functions through sovereignty, treaty law, custom, codification, courts, and institutions.

3. Roman Law and Ius Gentium

Roman law occupies an unusual place in the history of international law. It did not create a modern interstate legal order, and it did not rest on sovereign equality. Rome was an imperial legal system, organised around citizenship, hierarchy, conquest, administration, commerce, and the authority of Roman institutions. Yet Roman law supplied later jurists with concepts, language, and methods that became central to European legal thought, natural law, private law, and the law of nations.

The most important Roman contribution was not a ready-made system of public international law. It was a legal vocabulary for thinking beyond one city’s internal law. The distinction between ius civile and ius gentium helped later writers imagine that some legal principles could operate across communities, even where local laws differed. That distinction did not make Rome a model of modern international law, but it gave later jurists a powerful intellectual tool.

3.1 Ius civile and ius gentium

Roman jurists distinguished ius civile, the law proper to Roman citizens, from ius gentium, a body of rules or principles associated with dealings involving foreigners and common practices among peoples. Gaius famously explained that every people governed by laws and customs used partly its own law and partly the law common to all peoples. The first was ius civile, the second was ius gentium (Gaius, Institutes, 1.1).

This distinction was practical before it became theoretical. Rome expanded through conquest, trade, diplomacy, migration, and administration. A legal order limited to Roman citizens could not manage the everyday problems created by foreigners, merchants, provincial communities, and cross-border transactions. Roman law needed rules that could handle sales, property, contracts, agency, possession, and liability in cases involving non-citizens.

The office of the praetor peregrinus, created to deal with disputes involving foreigners, illustrates this practical need. Roman legal institutions had to produce workable rules for mixed legal relationships. These rules did not abolish the difference between Romans and non-Romans, but they created techniques for legal interaction across status lines. The result was not equality, but legal manageability (Buckland, 1963).

The doctrinal importance of ius gentium lies in its later reception. Medieval and early modern jurists read Roman categories through canon law, natural law, theology, and scholastic philosophy. Over time, ius gentium became part of the intellectual background for the law of nations. The Roman term changed meaning as it moved across periods. In Roman law, it was not identical with modern international law. In later European thought, it became one of the linguistic bridges between Roman legal universalism and rules governing relations among political communities (Schiller, 1978).

This difference matters. If ius gentium is treated as modern international law, the history becomes inaccurate. Rome did not operate through a society of equal sovereign states. It did not accept a general principle of non-intervention, and it did not recognise foreign polities as legal equals. Yet if ius gentium is ignored, the history also becomes weak. Later jurists used Roman legal language to organise arguments about natural reason, commerce, war, property, and legal obligation beyond local law.

3.2 Empire and legal hierarchy

The Roman legal order was imperial. It was not built on horizontal relations among equal political communities. Rome absorbed, subordinated, negotiated with, and administered other peoples through a system centred on Roman power. Legal status depended on citizenship, location, political relationship to Rome, and imperial authority.

This hierarchy makes Rome very different from the modern image of international law as law between sovereign states. Rome did not treat other communities as coequal legal persons. It could enter treaties, make alliances, receive envoys, and recognise local arrangements, but those practices existed inside a wider imperial imagination. Rome’s legal world was shaped by domination, incorporation, and graded status, not by universal sovereign equality (Watson, 1992).

The grant of Roman citizenship also shows the imperial character of the system. Citizenship was not merely a private legal category. It marked political membership, privilege, procedural protection, and access to Roman legal remedies. The Constitutio Antoniniana of 212 CE, which extended Roman citizenship broadly across the empire, did not create equality between independent peoples. It expanded imperial citizenship within Roman authority (Sherwin-White, 1973).

This point is essential for legal accuracy. Roman law influenced later jurists because it offered refined legal concepts, not because it gave them a model of international legal equality. The Roman juristic method, with its attention to categories, definitions, remedies, interpretation, and legal reasoning, became central to European legal education. But the political structure behind that law remained imperial.

The legacy is double. Roman law helped later scholars think about common legal principles, natural reason, contracts, property, obligation, and legal personality. At the same time, its imperial background reminds readers that legal universality can coexist with hierarchy. A legal system may claim broad rational authority, while still organising unequal relations between centre and periphery.

3.3 Citizenship, foreigners, and commerce

Roman law dealt with foreigners through a combination of status, jurisdiction, and practical legal adaptation. Non-citizens did not automatically enjoy the full protections of ius civile, but they were not legally invisible. Roman institutions developed methods to regulate transactions involving foreigners, especially in commercial life.

Commerce made rigid legal separation impractical. Merchants needed rules for sale, debt, partnership, carriage, property, and dispute settlement. Roman law responded by developing forms of legal reasoning that could operate across status differences. This practical flexibility later helped Roman law become attractive to medieval and early modern jurists, especially in commercial and private law contexts.

Property is a useful example. Roman law developed sophisticated distinctions between possession, ownership, transfer, usufruct, servitudes, and obligations. These categories later shaped European private law, and indirectly influenced international legal debates about territory, occupation, acquisition, title, and control. The movement was not direct, but the conceptual influence was real.

The same applies to a contract. Roman ideas of agreement, good faith, obligation, and legal remedy later entered broader legal thought. In early modern Europe, jurists used Roman and natural law concepts to discuss treaties, promises, commercial rights, and sovereign commitments. The law of nations drew heavily on this inherited vocabulary, even when it addressed problems that Roman law had not treated as interstate law.

Roman law also influenced the method of legal scholarship. It trained jurists to classify legal problems, distinguish categories, interpret texts, and connect rules to remedies. That method mattered for the later development of international law as an academic discipline. The vocabulary of ius gentium, the logic of obligation, and the habit of systematic legal reasoning all helped build the intellectual environment in which later writers, including Vitoria, Grotius, Pufendorf, and Vattel, worked.

The Roman legacy should be stated with precision. Rome did not give the world modern international law. It gave later lawyers tools for thinking about law beyond local citizenship, law across communities, and law as a disciplined form of reasoning. Those tools survived because they could be adapted to new political problems.

4. Religion, Natural Law, and Just War

Religion and natural law shaped international legal thought before the rise of modern positivism. Medieval and early modern lawyers did not usually begin with state consent as the sole source of legal obligation. They worked with divine law, natural law, canon law, Roman law, custom, royal authority, papal claims, imperial claims, and moral theology. In that world, law was not only a product of political will. It was also linked to moral order.

The central legal problem was war. Medieval law did not prohibit war as such. It asked when war could be justified, who could authorise it, what cause could support it, and how violence should be conducted. This made just-war doctrine one of the most important bridges between theology, moral philosophy, and later international law.

4.1 Christian just-war doctrine

Christian just-war doctrine developed through several layers of thought. Augustine supplied a major starting point by arguing that war could be morally permissible when directed toward peace, order, and the punishment of wrong. War was not praised, but it was not absolutely forbidden. The moral question was whether violence could be used under legitimate authority, for a just cause, and with a proper intention (Augustine, 1998).

Aquinas later gave the doctrine a more systematic form. In the Summa Theologiae, he identified three conditions for a just war: authority of a ruler, just cause, and right intention. These conditions became central to later Christian legal and theological writing on war (Aquinas, 1947). They did not create a modern prohibition on force. They created a framework for judging war within a moral and legal order.

Canon law also mattered. It organised ideas about authority, sin, punishment, peace, clerical immunity, oaths, truces, and the moral limits of violence. The Church did not eliminate war, but it helped create categories through which war could be judged. The Peace of God and Truce of God movements, for example, tried to protect certain persons, places, and times from violence. Their practical success was limited, but their legal imagination was important.

The Christian just-war tradition shaped later debates about conquest, intervention, punishment, defence, and lawful authority. Spanish scholastics, especially Vitoria and Suárez, inherited this tradition and adapted it to the problems created by Iberian expansion. Grotius also worked in a world still marked by just-war reasoning, even as he tried to systematise the law of war and peace in a broader legal language.

The legal point is clear. Medieval Christian doctrine did not make war illegal. It made war legally and morally accountable. That difference is fundamental. The law asked who could wage war, why war could be waged, and which purposes could justify armed force. Only much later would international law move toward the Charter model, where the starting point is the prohibition of force.

4.2 Islamic law and restraints on war

Islamic legal traditions also developed rules on war, diplomacy, truces, protection, and the treatment of non-combatants. These traditions are essential to a balanced history of international law because they show that legal restraints on violence did not emerge only within Christian Europe.

Classical Islamic jurists discussed war within a legal and moral framework shaped by the Qur’an, hadith, juristic reasoning, political authority, and the practice of Muslim rulers. They addressed questions of lawful authority, treaties, safe conduct, protection of envoys, truces, prisoners, property, and the treatment of civilians. The vocabulary differed from Christian just-war doctrine, but the basic legal concern was similar: violence required limits (Khadduri, 1966).

The reported instructions associated with Abu Bakr are often cited as an early example of restraint in warfare. They include prohibitions against treachery, mutilation, killing children, women, and elderly persons, and destroying fruitful trees, except for necessity. The historical transmission and interpretation of such instructions must be handled carefully, but their legal significance lies in the broader tradition of restraint that they represent (Aboul-Enein and Zuhur, 2004).

Islamic law also developed doctrines of aman, or safe conduct, which could protect foreigners, traders, envoys, and enemies under certain conditions. Truces and agreements were recognised as legally significant, and diplomatic communication had to be protected for relations to function. These rules complicate any history that treats Europe as the sole site of legal sophistication.

This section should not romanticise Islamic legal history, just as Christian legal history should not be romanticised. Practice often departed from doctrine. Muslim polities, like Christian polities, fought wars, conquered territory, enslaved captives, and pursued political power. The legal point is not that one tradition was morally pure. The point is that Islamic jurists developed legal categories for restraining violence, regulating relations with outsiders, and managing conflict.

Including Islamic law also improves doctrinal understanding. It shows that rules on war, envoys, truces, captives, and protected persons developed in multiple legal cultures. Modern international humanitarian law did not simply descend from one civilisational source. It later codified and universalised rules through treaties, customs, institutions, and humanitarian practice, but older traditions had already addressed many of the same moral and legal problems.

4.3 Medieval universal authority

The medieval legal order was not built around sovereign equality. Authority was layered, contested, and hierarchical. Kings, emperors, popes, bishops, cities, feudal lords, universities, and corporate bodies all claimed forms of legal authority. The idea of one territorially exclusive sovereign state had not yet become the organising principle of European order.

The papacy claimed spiritual authority with legal consequences. The Holy Roman Empire claimed a universal or quasi-universal political role, even when its practical power was limited. Canon law operated across territories and affected marriage, clerical status, oaths, procedure, moral discipline, and relations between rulers. Roman law, revived in medieval universities, supplied legal categories that could be used across local jurisdictions.

This world was plural, not anarchic. It contained overlapping jurisdictions, legal forums, privileges, immunities, and hierarchies. Authority did not flow only through territory. It also flowed through status, office, religious jurisdiction, feudal relationship, corporate privilege, and universal claims. That structure is difficult to reconcile with the later Westphalian image of equal territorial states.

The medieval Christian commonwealth also shaped attitudes toward outsiders. Legal and theological distinctions between Christians, Muslims, Jews, pagans, heretics, and infidels affected war, trade, conversion, protection, and toleration. These categories later influenced debates on conquest and the legal status of non-European peoples. The colonial encounter did not arise in a legal vacuum. It drew on inherited medieval distinctions, even as early modern jurists revised them.

Modern sovereign equality developed partly against this older order. The rise of territorial monarchy, religious conflict, Reformation politics, commercial expansion, and diplomatic practice weakened claims of universal papal or imperial supremacy. Later, international law would place states at the centre. But the older medieval structure matters, because it shows what modern sovereignty replaced: overlapping authority, religious hierarchy, and universal claims to legal order.

4.4 War as regulated violence

The major doctrinal difference between medieval law and modern international law lies in the legal treatment of war. Medieval and early modern law mainly asked when war could be just. Modern law, especially after 1945, begins with a different premise: force is prohibited, except in narrow legal circumstances.

This shift should not be understated. Under just-war doctrine, the central inquiry is concerned with lawful authority, just cause, and right intention. A ruler could wage war if the war satisfied moral and legal criteria. The law did not treat armed force as presumptively unlawful in the modern Charter sense. It treated war as a grave act that required justification.

The UN Charter changed the legal structure. Article 2(4) prohibits the threat or use of force against the territorial integrity or political independence of any state, or in any other manner inconsistent with the purposes of the United Nations. Article 51 preserves the inherent right of self-defence if an armed attack occurs, and Chapter VII gives the Security Council authority to authorise enforcement measures. The result is a legal order in which war is no longer an ordinary instrument of policy.

Yet older just-war ideas did not disappear completely. They still influence moral and political arguments about humanitarian intervention, self-defence, necessity, proportionality, aggression, and civilian protection. The language changed, the institutions changed, and the doctrine changed, but the problem remained: law must decide how to judge organised violence.

The difference between jus ad bellum and jus in bello is central here. Jus ad bellum concerns the legality of resorting to force. Jus in bello, or international humanitarian law, governs conduct during armed conflict, regardless of which side was legally entitled to use force. Medieval just-war thinking often blended these questions. Modern law separates them more sharply. A state may fight an unlawful war, yet its soldiers and commanders remain bound by humanitarian rules. A state acting in lawful self-defence must still respect the law of armed conflict.

This development shows why religion, natural law, and just-war doctrine belong in the history of international law. They did not create the modern Charter system, but they supplied centuries of argument about authority, violence, justice, restraint, and responsibility. Later, international law transformed those questions through sovereignty, positivism, codification, and institutions.

5. Iberian Expansion and Global Encounter

Iberian expansion marks one of the decisive turning points in the history of International Law, because it forced European jurists to confront questions that older European legal categories could not answer easily. Could Christian rulers divide overseas territories between themselves? Did papal authority create a valid title over lands inhabited by non-Christian peoples? Could discovery, occupation, conquest, or conversion justify dominion? Did Indigenous peoples possess legal personality, political authority, property, and rights under natural law?

These questions were not theoretical luxuries. They arose in the context of conquest, forced conversion, Atlantic navigation, extraction, slavery, territorial acquisition, and imperial rivalry. Law was used to restrain certain forms of violence, but it was also used to organise domination. The colonial encounter, for that reason, was not a peripheral episode in international legal history. It helped shape doctrines of sovereignty, title, jurisdiction, commerce, intervention, and legal personality (Anghie, 2005).

5.1 Treaty of Tordesillas

The Treaty of Tordesillas, concluded in 1494 between Castile and Portugal, divided overseas spheres of expansion between the two Iberian crowns. It adjusted the line previously associated with papal intervention, and it sought to manage rivalry between two Christian powers competing over Atlantic routes, African trade, and newly claimed lands across the ocean.

The treaty’s legal significance lies less in its technical boundary and more in what it assumed. Spain and Portugal treated distant territories as objects capable of allocation between European monarchs. Indigenous peoples, their laws, their political communities, and their territorial relationships were not treated as sources of consent. The agreement was bilateral, European, dynastic, and Christian. It was not a universal settlement, and it did not express a general law accepted by all peoples affected by it.

This point matters because the treaty shows how legal form could make imperial ambition appear orderly. A diplomatic agreement between two European crowns became a legal technique for reducing conflict between colonising powers, while leaving the people most affected outside the legal conversation. The treaty created peace between competitors, not justice for those whose lands were being claimed.

Tordesillas also reveals the limits of treating early modern treaty practice as evidence of sovereign equality. Spain and Portugal dealt with each other as Christian monarchies capable of reciprocal commitment. They did not extend that same legal status to the Indigenous peoples whose territories entered the imperial map. Equality, at this stage, operated inside a restricted European-Christian circle.

The treaty also prepared later debates about title and occupation. If papal authority and bilateral agreement were insufficient, European jurists needed other arguments to justify control. That need helps explain the later importance of discovery, occupation, conquest, commerce, evangelisation, and natural law. The Iberian division of overseas claims created legal problems that the School of Salamanca and later writers could not avoid.

5.2 Papal authority and title to territory

Papal bulls played a major role in the legal language of Iberian expansion. Instruments such as Dum Diversas, Romanus Pontifex, and Inter caetera were used to support claims of Christian dominion, missionary authority, and overseas expansion. They did not function as modern treaties, but they carried legal and theological force inside the Latin Christian world.

The central issue was the title. European powers needed arguments explaining how authority could be acquired over lands already inhabited by organised communities. Papal donation, discovery, conquest, occupation, and conversion became part of the vocabulary through which territorial claims were framed. Each argument tried to convert political expansion into legal entitlement.

Discovery was especially important, but also deeply unstable. If land was inhabited, discovery alone could not easily justify ownership without denying the legal personality of those already there. Occupation faced a similar problem. In Roman law and later European doctrine, occupation could support title over things belonging to no one. Applying that logic to inhabited lands required treating non-European territories as legally deficient, vacant, or insufficiently governed by European standards.

Conversion also carried legal consequences. Christian rulers and theologians debated whether refusal to accept Christianity could justify war or dominion. More careful jurists rejected automatic conquest on religious grounds, yet missionary language still helped place non-Christian peoples inside a hierarchy of judgment. Their political and legal systems could be evaluated, corrected, or punished by reference to supposedly universal norms.

This is where legal language performed its most dangerous work. It did not simply describe conquest after the fact. It helped make conquest intelligible, defensible, and administrable. Claims of title, jurisdiction, protection, and conversion turned violence into a legal programme. The vocabulary of law gave the empire a structure, a procedure, and a moral grammar (Muldoon, 1979; Pagden, 1995).

5.3 Vitoria and Indigenous peoples

Francisco de Vitoria is one of the most important and most difficult figures in this part of the history of international law. His lectures on the Indies rejected several crude justifications for Spanish dominion. He denied that the emperor, by himself, had universal authority over the world. He also denied that the pope could simply transfer ownership of Indigenous lands to Spanish rulers. Most importantly, he recognised that Indigenous peoples had reason, property, political communities, and forms of legal authority (Vitoria, 1991).

That recognition was significant. Vitoria’s argument made it harder to defend conquest merely by saying that non-Christian peoples lacked legal status. He treated the Indigenous peoples of the Americas as participants in a broader normative order, not as animals, things, or legally empty obstacles. This placed limits on some imperial claims, and it exposed the weakness of direct papal donation as a complete title.

Yet Vitoria’s framework also opened other routes to intervention. He argued that Spaniards possessed rights of travel, communication, trade, and preaching under the law of nations. If Indigenous peoples prevented those rights, the Spanish war could become legally arguable. He also allowed intervention in cases involving alleged violations of natural law, such as practices that European theologians condemned as grave wrongdoing.

This is the double role of Vitoria’s legal thought. It restrained the empire by rejecting some of its broadest claims. At the same time, it reorganised the empire through a more refined legal language. Spanish authority could no longer rest simply on papal gift or religious superiority, but it could be defended through universal rights, commerce, communication, missionary access, and punishment of alleged wrongs (Anghie, 2005).

For that reason, Vitoria should not be presented as a pure defender of Indigenous peoples. That reading is too generous. Nor should he be reduced to a simple apologist for conquest. That reading is too flat. His importance lies in the tension. He made Indigenous legal personality visible, while also placing Indigenous communities under a universal legal framework largely articulated by European theologians.

This tension remains central to international law. Universal language can protect vulnerable people, but it can also authorise intervention, discipline, and judgment. Vitoria’s work shows how legal universalism may operate as both shield and instrument of hierarchy.

5.4 Salamanca and natural law

The School of Salamanca developed legal and theological arguments that deeply influenced early modern thought on war, sovereignty, property, trade, and the law of peoples. Its writers, including Vitoria, Domingo de Soto, Martín de Azpilcueta, and Francisco Suárez, worked inside a scholastic tradition shaped by Roman law, canon law, Aristotle, Aquinas, and the practical crises created by Iberian expansion.

Their importance lies in the reworking of natural law. Salamanca writers treated natural law as a rational order that applied to all human beings, not only Christians. This could support claims about Indigenous property, political authority, and moral equality. It could also support limits on unjust war, arbitrary domination, and purely religious conquest.

Yet the same universalism created risks. If natural law applied to all peoples, European jurists could claim authority to identify violations of that law everywhere. They could condemn Indigenous practices, judge non-European institutions, and justify intervention when they believed universal norms had been breached. The result was a legal structure that recognised common humanity, but often under European interpretive control.

Suárez later contributed to debates about law, sovereignty, political authority, and the binding force of norms among peoples. His work helped move scholastic legal thought toward a more systematic account of relations between political communities. Yet this movement did not produce a modern law of equal states. It remained tied to theology, monarchy, empire, and hierarchical assumptions about civilisation and religion.

Salamanca’s place in international legal history is, for that reason, complex. It gave later lawyers important arguments about natural rights, just war, the law of peoples, and limits on authority. It also shows how universal legal reasoning could accompany colonial expansion. The lesson is not that natural law was either emancipatory or imperial. It was both, depending on who interpreted it, who enforced it, and whose world was being judged.

6. Grotius, Commerce, and the Sea

Grotius belongs near the centre of any serious account of early modern international law, but not because he single-handedly created the discipline. His importance lies in the way he systematised legal arguments about war, peace, commerce, navigation, property, and the sea, at a moment when European power was expanding through trade, naval force, chartered companies, and colonial competition.

The traditional image of Grotius as a detached philosopher of peace is incomplete. He wrote in a world shaped by the Dutch revolt against Spain, maritime conflict with Portugal, commercial expansion in Asia, and the rise of the Dutch East India Company. His legal arguments were connected to concrete disputes over trade routes, prize-taking, monopoly claims, and the legitimacy of violence at sea (van Ittersum, 2006).

6.1 Grotius and the Dutch East India Company

Grotius’s early legal work was closely connected to the Dutch East India Company, known as the VOC. The company was not an ordinary merchant body. It possessed public powers, including the capacity to wage war, make agreements, seize ships, establish forts, and govern trading posts. It stood at the boundary between private commerce and public authority.

The immediate background was the seizure of the Portuguese vessel Santa Catarina by Dutch forces in 1603. The incident raised a difficult legal question: could a private company, acting under Dutch authority, lawfully capture a Portuguese ship in Asian waters? Grotius wrote to defend the legality of Dutch action, and his broader manuscript, De iure praedae, developed arguments about natural law, commerce, punishment, prize, and maritime freedom (van Ittersum, 2006).

This context changes how Grotius should be read. His legal thought did not emerge only out of abstract concern for peace among states. It emerged through a dispute involving corporate violence, maritime commerce, imperial rivalry, and the legal status of European action outside Europe. The law of nations was being shaped by lawyers advising actors with direct material interests.

The VOC context also shows how early modern legal authority was not confined to states. Chartered companies exercised powers that looked public, but served commercial ends. They negotiated, fought, governed, and claimed legal justification. This complicates the later image of international law as a law made only by states and for states.

Grotius’s role, then, was not simply to humanise international relations. He helped provide legal vocabulary for a world where trade and violence were deeply connected. His work shows how international law developed not only through diplomacy and treaties, but also through legal opinions, commercial disputes, naval warfare, and corporate expansion.

6.2 Mare liberum and maritime freedom

Mare liberum, published in 1609, argued that the sea could not be appropriated in the same way as land. Grotius claimed that the ocean was open to navigation and trade, and that no state could lawfully monopolise the high seas. The argument directly challenged Iberian claims over maritime routes and overseas commerce.

The doctrine of maritime freedom had a powerful legal appeal. The sea appeared vast, fluid, and resistant to occupation. Unlike land, it could not easily be possessed, enclosed, cultivated, or permanently controlled. Grotius used this physical difference to support a legal distinction between territory and ocean space. Navigation and commerce, in his argument, belonged to a wider legal order of common use (Grotius, 2004).

Yet maritime freedom was not politically neutral. It served Dutch interests against Portuguese and Spanish monopoly claims. Freedom of the seas was, in practice, a doctrine of commercial access. It allowed rising maritime powers to contest older empires that had tried to close routes through papal authority, treaty division, and naval control.

The later history of the sea shows how durable the problem became. Coastal states claimed territorial seas for security and control. Naval powers defended freedom of navigation. Commercial powers used maritime law to protect trade. Later, technological change and resource extraction produced new claims over continental shelves, exclusive economic zones, fisheries, seabed minerals, and marine scientific research.

This makes Mare liberum more than an early modern pamphlet. It introduced a debate that still shapes international law: how should law divide ocean space between common use, coastal authority, security interests, commercial freedom, and shared resources? Modern law of the sea no longer follows Grotius in pure form, but it still works inside a field of tension that his argument helped define.

6.3 War, trade, and legal justification

Early modern international law developed in a world where war and trade were not separate spheres. Commercial expansion required ships, forts, armed convoys, monopoly rights, and coercive bargaining. Naval violence could be described as defence, reprisal, punishment, prize-taking, or lawful war. Legal categories gave structure to violence that served economic ends.

Privateering and prize law were especially important. Capturing enemy property at sea was not treated simply as piracy if done under lawful authority. Letters of marque, admiralty proceedings, and prize adjudication turned maritime violence into a legal process. The distinction between pirate, privateer, merchant, and naval actor was often legally decisive, even when the conduct looked similar on the water.

Grotius’s arguments must be placed inside this legal world. He tried to show that Dutch actions against Portuguese interests could be justified by natural law, injured rights, denial of trade, and lawful punishment. Commerce was not merely an economic activity. It became a legal right, and interference with it could be framed as a wrong capable of supporting coercive action.

This matters for the history of international law because it exposes a common misunderstanding. International law did not develop only through peaceful conferences, academic treatises, or judicial decisions. It also developed through conflict over ships, cargo, ports, monopolies, charters, routes, and colonial markets. Legal doctrine often followed the movement of capital and armed force.

The connection between war and trade also shaped later doctrines. Neutrality, blockade, contraband, freedom of navigation, prize, piracy, maritime jurisdiction, and protection of commerce all grew out of this unstable relationship. Early modern legal argument did not merely regulate state conduct. It helped organise the legal infrastructure of global commerce.

6.4 Grotius beyond the founding myth

Calling Grotius “the father of international law” is attractive, but misleading. It gives the discipline a clear ancestor, a respectable origin, and a humanist identity. It also simplifies a much longer and more contested history. International law did not come from one author, one book, one civilisation, or one moment.

Grotius matters because he gave systematic form to legal arguments about war, peace, commerce, punishment, and the sea. He worked with natural law, Roman law, theology, state practice, classical sources, and practical disputes. His writing helped later jurists think about legal obligation beyond domestic law, especially where no common superior existed.

Yet Grotius also reflected the power struggles of his own world. His work served Dutch commercial and maritime interests. It was tied to corporate expansion, imperial rivalry, and legal justification for violence outside Europe. Reading him only as a humanitarian founder hides that political and economic context.

A better reading places Grotius among several formative figures and traditions: Vitoria, Suárez, Gentili, Pufendorf, Vattel, Roman law, canon law, scholastic natural law, maritime custom, Islamic and other non-European legal traditions, diplomatic practice, and colonial encounter. This does not reduce Grotius’s importance. It makes his importance more accurate.

The strongest conclusion is that Grotius was not the origin of international law, but one of its major systematisers. He helped turn scattered arguments about war, commerce, sovereignty, and the sea into a legal language that later scholars could inherit, revise, and contest. His place in the history of international law is secure, but it should be freed from mythology.

7. Westphalia and Sovereign Statehood

The Peace of Westphalia occupies a central place in the history of International Law, but its importance is often overstated. The treaties of Münster and Osnabrück, concluded in 1648, ended the Thirty Years’ War within the Holy Roman Empire and formed part of a wider European settlement. They addressed religion, territory, imperial estates, foreign guarantees, and the political balance within a fragmented European order.

The common textbook story says that Westphalia created modern sovereignty. That story is useful as a symbol, but weak as history. Sovereignty did not appear suddenly in 1648, and the treaties did not establish a universal system of equal states. The modern state developed through a longer process involving war, taxation, administration, diplomacy, territorial consolidation, religious conflict, and legal theory (Osiander, 2001).

Westphalia matters because later lawyers used it to tell a powerful story about international order. It became shorthand for territorial authority, non-intervention, state consent, and the decline of universal papal or imperial supremacy. Its legal memory became almost as important as the settlement itself.

7.1 Westphalia as symbol and myth

Westphalia was not the birth certificate of international law. It did not use the modern vocabulary of sovereign equality in the way later lawyers imagined, nor did it create a clean separation between domestic and international authority. The Holy Roman Empire remained legally complex, with overlapping jurisdictions, imperial rights, religious guarantees, and foreign powers involved in the settlement.

The myth became influential because it gave international law a simple origin. It allowed lawyers to say that medieval hierarchy had given way to a modern order of territorial states. That story was attractive, especially for a discipline that needed a clear foundation. It linked international law to peace, order, statehood, and secular authority.

Yet the symbolic use of Westphalia hides the slow and uneven character of legal change. Territorial authority had been developing before 1648, and universal claims did not disappear after it. Dynastic politics, imperial claims, religious authority, colonial domination, and great-power management continued to shape legal order. The world after Westphalia was not a world of equal sovereigns. It was a European order still marked by hierarchy, empire, and exclusion (Krasner, 1999).

The better reading is more precise. Westphalia did not create modern international law, but it became a legal memory through which modern international law explained itself. It helped later scholars and diplomats frame sovereignty as territorial authority, and it gave the discipline a convenient starting point for a state-centred narrative.

7.2 Territorial authority

The rise of territorial authority was one of the most important changes in the early modern legal order. Political power increasingly became tied to defined territory, regular administration, taxation, military organisation, and external representation. A ruler’s authority was no longer understood only through personal allegiance, dynastic right, religious hierarchy, or feudal relationship. It became increasingly attached to territorial control.

This change mattered legally. A political community that controlled territory could make treaties, police borders, raise armies, collect revenue, administer justice, and claim jurisdiction over persons and property within its domain. Territorial rule made the state more visible as a legal actor. It allowed external relations to be organised around entities that could commit, perform, breach, and answer for obligations.

The modern state became dominant not because it was morally superior, but because it solved practical problems of authority. It could centralise coercion, standardise administration, negotiate externally, and impose internal order more effectively than many older arrangements. International law developed alongside this process because legal relations between states required identifiable units capable of representation and responsibility.

Territorial authority also shaped jurisdiction. The idea that a state has primary authority within its territory became one of the core assumptions of modern international law. Later doctrines of territorial sovereignty, non-intervention, territorial integrity, diplomatic relations, and state responsibility all depend on this basic structure.

Yet territorial authority was never absolute. Trade, religion, dynastic claims, minorities, foreign guarantees, navigation rights, capitulations, and later human rights all challenged the idea that territory could seal a state from external legal concern. The history of sovereignty is not a history of perfect autonomy. It is a history of authority constantly asserted, limited, negotiated, and breached.

7.3 Sovereign equality

Sovereign equality is one of the central doctrines of modern international law. It means that states, as legal persons, possess equal basic status under international law, regardless of size, wealth, military capacity, population, or political influence. The doctrine supports treaty capacity, recognition, jurisdiction, immunity, diplomatic relations, and responsibility.

The emergence of states as legal persons was a major conceptual shift. Medieval and early modern legal orders often focused on rulers, dynasties, empires, cities, churches, estates, and corporate bodies. Modern international law increasingly treated the state as a continuing legal entity, distinct from the person of the ruler. This mattered for treaties, succession, debt, war, neutrality, recognition, and responsibility.

Sovereign equality also gave international law a formal structure. If states were legal equals, no state could claim ordinary legal authority over another without consent or a recognised legal basis. This supported principles such as non-intervention, immunity, and the need for consent in treaty obligations. It also helped distinguish international law from imperial command.

The doctrine, however, has always contained tension. Formal equality can coexist with material inequality. A small state and a great power may be equal in legal personality, but not in military, economic, diplomatic, or institutional influence. Great powers have repeatedly shaped the legal order while speaking the language of equality. The Security Council’s permanent membership and veto later made this tension visible inside the UN Charter system.

Sovereign equality should, for that reason, be read as both a legal achievement and a legal fiction. It protects weaker states by denying formal hierarchy among states. At the same time, it may conceal the unequal conditions under which states negotiate, litigate, borrow, trade, and defend themselves. Simpson describes this problem as one of the enduring tensions between formal equality and legalised hierarchy in international society (Simpson, 2004).

7.4 Limits of the Westphalian model

The greatest weakness of the Westphalian model is that it describes European relations more easily than global legal history. Even inside Europe, sovereignty was uneven, contested, and limited. Outside Europe, the model becomes still more problematic. European states claimed equality among themselves, while denying equal legal standing to many non-European peoples and political communities.

This contradiction is central to the history of international law. European powers defended territorial sovereignty at home, yet claimed overseas territories through discovery, occupation, conquest, protectorates, chartered companies, unequal treaties, and mandates. The language of sovereign equality did not prevent the empire. It often operated beside it.

Colonialism reveals the limits of any simple Westphalian narrative. If the post-1648 order was truly based on equal territorial states, the legal subordination of Africa, Asia, the Americas, and Oceania becomes difficult to explain. A more accurate account recognises that international law developed through two connected structures: equality among recognised European states, and hierarchy toward peoples treated as outside, below, or not yet ready for full legal membership (Anghie, 2005).

The Westphalian model also obscures actors that did not fit the state form. Indigenous peoples, empires, trading companies, religious authorities, cities, minorities, and transnational commercial networks all played roles in legal history. A state-centred account can explain much, but not everything.

Westphalia remains important, but it should be used carefully. It is best understood as a powerful symbol of territorial statehood, not as the full origin of modern international law. Its value lies in showing how international lawyers later imagined the state system, and its danger lies in making that imagination look universal.

8. Enlightenment and the Law of Nations

The Enlightenment did not replace older legal ideas in one movement. Natural law, Roman law, treaty practice, diplomacy, commerce, dynastic politics, and balance-of-power thinking continued to overlap. Yet the eighteenth century gave the law of nations a more practical and state-centred form. Writers increasingly treated states as the main legal actors, sovereignty as the organising principle, and consent as a central basis of obligation.

This period is important because it translated earlier theological and natural law arguments into a language more suited to diplomacy. The law of nations became less dependent on universal religious authority and more connected to state interest, treaties, neutrality, commerce, war, and the European political order. It did not become fully positivist, but it moved in that direction.

8.1 Vattel and the state as moral person

Emmer de Vattel was one of the most influential writers of the eighteenth-century law of nations. His work, The Law of Nations, published in 1758, helped make the state the central legal subject of international legal thought. Vattel described nations or states as moral persons, capable of rights, duties, consent, self-preservation, independence, and external relations (Vattel, 2008).

This language mattered because it made international law more usable for diplomats and rulers. Vattel’s law of nations was not only a philosophical system. It was a practical guide to sovereignty, treaty-making, neutrality, war, commerce, and state interest. His writing became influential because it spoke to the needs of a world of territorial states, imperial rivalry, and expanding diplomacy.

The idea of the state as a moral person also helped separate the state from the ruler. A king could die, a dynasty could change, and a government could fall, but the state could continue as a legal person. That distinction later became central to treaty continuity, state responsibility, recognition, succession, and public debt.

Vattel’s thought also linked sovereignty with independence. A state, in his account, had the right to govern itself and pursue its preservation. This helped strengthen non-intervention as a legal principle, at least among recognised states. Yet the protection was not applied equally. European legal thought often reserved full respect for states considered civilised, while treating non-European polities through hierarchy, tutelage, or exclusion.

Vattel’s importance lies in this practical consolidation. He did not invent the law of nations, but he made it legible as a law of states. His work became a bridge between natural law and the later positivist tradition.

8.2 Consent and positive law

The eighteenth century also saw a gradual movement toward positive law. Legal obligation became more closely associated with the will, practice, and agreement of states. Natural law did not disappear, but treaties, custom, diplomatic practice, and recognised usage became increasingly important.

Consent gave international law a practical foundation. If states were independent, and no superior authority stood above them, obligations had to be explained through agreement, custom, or accepted rules of conduct. This made treaties central. It also made diplomatic practice and state conduct more important as evidence of law.

The movement toward positivism had advantages. It made international law more concrete, more technical, and more closely connected to actual state behaviour. It reduced reliance on broad moral claims, and it gave lawyers a clearer method for identifying rules. Later positivist lawyers would build on this tendency by emphasising state will, sources, recognition, and consent.

The cost was serious. If law depends mainly on the consent of recognised states, those excluded from recognition may be excluded from law-making. If only certain states count as full participants, then consent becomes a privilege of the powerful. This problem became sharper in the nineteenth century, when positivism combined with the standard of civilisation.

Consent also created a lasting doctrinal tension. International law claims to bind states, but it often explains its binding force through state acceptance. That creates difficulty when law seeks to limit powerful states, protect individuals, prohibit aggression, or recognise peremptory norms. The later rise of jus cogens, human rights, and obligations owed to the international community challenged the idea that consent alone could explain the whole system.

8.3 Balance of power

The balance of power was one of the main legal-political techniques of eighteenth-century Europe. It was not a doctrine of moral equality. It was a method for managing rivalry among major powers, preventing domination by one state, preserving territorial settlements, and organising diplomatic bargaining.

The balance of power worked through treaties, alliances, territorial compensation, dynastic settlements, recognition, neutrality, and congress diplomacy. It treated Europe as a political system whose stability required adjustment. Legal agreements did not merely record power. They helped organise it.

The Treaty of Utrecht, the settlement of Vienna, and later congress diplomacy reflected this logic. Territorial transfers, guarantees, buffer arrangements, and recognition decisions were used to maintain equilibrium. Law gave form to political compromise, while political necessity shaped legal outcomes (Lesaffer, 2004).

This produced a disciplined but unequal order. Great powers claimed responsibility for European stability, and smaller states often had to live with decisions made above them. The balance of power reduced some risks of hegemony, but it also legitimised intervention, territorial bargaining, and great-power management.

The balance of power also shaped the later development of collective security. The League of Nations and the United Nations rejected the balance of power as a sufficient basis for peace, but they inherited the problem it tried to solve: how can law manage power without becoming only the language of power? The Security Council, with permanent members and veto power, shows that great-power management survived inside a more institutional legal form.

8.4 Europe’s public law

The idea of a European public law, often described as the public law of Europe, referred to a legal-political order made through treaties, diplomacy, dynastic rules, territorial settlements, and shared assumptions about European civilisation. It was not a universal legal system. It was a regional order that European jurists often treated as if it represented the highest form of legal development.

This European public law shaped doctrines of recognition, neutrality, treaty obligation, diplomatic rank, territorial settlement, and intervention. It also reinforced the idea that Europe had a special legal identity. European states could disagree, fight, and bargain, but they increasingly imagined themselves as members of a common legal and diplomatic society.

The problem was exclusion. Non-European polities were often measured against European standards before being admitted to full legal personality. Some were treated as unequal treaty partners, some as protectorates, some as objects of commerce or intervention, and others as territories available for occupation or colonial administration. Europe’s public law became a standard by which the rest of the world was judged.

This is why the Enlightenment law of nations must be read critically. It helped refine sovereignty, treaty practice, neutrality, and state personality. It also helped build a legal imagination in which Europe represented order, reason, civilisation, and progress. Non-European societies were often placed outside that circle, or admitted only on unequal terms.

The legal legacy is mixed. The Enlightenment made international law more practical, state-centred, and diplomatic. It prepared the ground for positivism, modern treaty practice, neutrality, and recognition. Yet it also carried assumptions that later supported hierarchy, empire, and the standard of civilisation. A serious history must keep both sides visible.

9. Nineteenth-Century Positivism and Empire

The nineteenth century transformed international law into a more technical, professional, and state-centred discipline. Treaties, custom, diplomatic practice, recognition, arbitration, and legal scholarship became more important than broad appeals to natural law. International lawyers increasingly presented their field as a positive legal order, grounded in the will and practice of states, rather than in universal moral reasoning alone.

That shift did not make international law neutral. It made the discipline more precise, but also more exclusionary. Full participation depended on being recognised as a “civilised” state, and that test was shaped by European assumptions about government, religion, commerce, property, diplomacy, and legal administration. The same century that strengthened arbitration and humanitarian law also produced protectorates, unequal treaties, colonial occupation, and legal doctrines that helped manage empire (Koskenniemi, 2001).

9.1 Positivism and the state will

Nineteenth-century positivism treated international law as a law made by states, especially through treaties, custom, and recognised practice. This marked a move away from earlier natural law arguments, which claimed authority through reason, divine order, or universal morality. Positivist lawyers wanted law to be identified through evidence: what states had agreed, what they had repeatedly done, and what they had accepted as legally binding.

This approach made international law more practical. Treaties could be read as formal commitments. Custom could be studied through diplomatic correspondence, state practice, judicial decisions, and official statements. Recognition could decide which political communities counted as states, which governments could represent them, and which entities could enter the legal community.

The professionalisation of international law also accelerated. Learned societies, journals, treatises, diplomatic manuals, arbitration practice, and university teaching gave the discipline a clearer technical identity. The Institut de Droit International, founded in 1873, reflected this new professional confidence. International law was no longer only a branch of moral philosophy or diplomacy. It became a specialised legal field, with its own vocabulary and methods (Koskenniemi, 2001).

The problem was the narrow circle of law-making authority. If law came mainly from the consent and practice of states, then only recognised states could fully participate in producing law. Non-European polities, Indigenous communities, colonised peoples, and entities considered “uncivilised” were often treated as objects of law rather than makers of law. Positivism, in practice, tied legal personality to recognition by the already recognised.

This created a deep contradiction. Positivism claimed to replace moral speculation with legal certainty, but the decision about who counted as a full legal subject often rested on political and civilisational judgment. The state will become central, but not every political community will be allowed to have a legally relevant will.

9.2 The standard of civilisation

The standard of civilisation was one of the most important doctrines in the history of International Law, because it controlled entry into the legal community. It was not a single treaty rule. It was a flexible legal and political test, used by European powers to decide which states could enjoy full legal personality, equal treaty relations, and immunity from colonial supervision or unequal arrangements.

The standard usually required a state to possess centralised government, stable administration, diplomatic capacity, protection for foreign nationals, respect for property, commercial openness, and legal institutions recognisable to European powers. These criteria appeared technical, but they carried civilisational assumptions. They measured non-European societies against European models of statehood, law, economy, and political order (Gong, 1984).

The doctrine created a hierarchy within a field that spoke the language of equality. States considered civilised could participate as legal equals. States considered semi-civilised could be admitted only partially, often through unequal treaties, extraterritorial privileges, or diplomatic restrictions. People considered uncivilised could be colonised, protected, administered, or excluded.

Its importance lies in its legal function. The standard of civilisation did not merely express prejudice. It organised legal consequences. It affected recognition, treaty relations, jurisdiction, sovereignty, intervention, territorial acquisition, and diplomatic protection. It gave European powers a language for deciding who could be trusted with sovereignty and who could be subjected to external control.

The doctrine also shaped later debates on development, governance, human rights, and state-building. The explicit vocabulary of civilisation lost legitimacy in the twentieth century, especially after decolonisation. Yet the habit of measuring states against external standards did not vanish. It reappeared, in different forms, through mandates, trusteeship, development policy, conditionality, governance benchmarks, and interventionist language.

9.3 Unequal treaties and capitulations

Unequal treaties show why treaty form does not always mean genuine equality. In classical doctrine, a treaty expresses consent between legal persons. In nineteenth-century practice, many treaties were concluded under military pressure, economic coercion, or diplomatic vulnerability. The document looked reciprocal, but the bargaining position was not.

China is the clearest example. After military defeat in the Opium Wars, China accepted treaties that opened ports, ceded territory, fixed tariffs, granted most-favoured-nation treatment, and allowed extraterritorial jurisdiction for foreign nationals. The Treaty of Nanking of 1842 and later agreements did not simply regulate relations. They reorganised China’s external legal position under pressure from imperial powers (Cassel, 2012).

The Ottoman Empire also lived under capitulatory arrangements, which gave foreign nationals privileges, consular jurisdiction, and commercial advantages. These arrangements had older roots, but in the nineteenth century they increasingly symbolised unequal legal status. Foreign states used them to limit Ottoman jurisdiction and protect their nationals from local courts.

Japan’s experience illustrates both subordination and legal adaptation. The treaties imposed after Commodore Perry’s expedition opened Japanese ports and created extraterritorial privileges. Japan later pursued legal reform, administrative centralisation, and diplomatic revision to escape unequal treaty status. Its eventual success showed that the standard of civilisation could be used as a ladder, but only by accepting the terms of those who controlled admission.

Unequal treaties reveal the weakness of formalism. A treaty may be valid in form, yet still reflect coercive inequality. International law did not always ignore that inequality; later doctrines on coercion, self-determination, and sovereign equality would challenge some of its effects. In the nineteenth century, however, treaty law often helped stabilise unequal relations under a legal surface.

9.4 The Berlin Conference

The Berlin Conference of 1884–1885 stands as one of the clearest examples of international law organising empire. European powers met to regulate colonial competition in Africa, especially in the Congo Basin and along major rivers. African political communities were not included as equal participants, even though the decisions concerned African territory, trade, sovereignty, and future administration.

The General Act of Berlin addressed freedom of trade in the Congo Basin, freedom of navigation on the Congo and Niger rivers, anti-slavery commitments, missionary access, and notification rules for future occupations on the African coast. Its legal vocabulary sounded orderly and humanitarian. It spoke of commerce, navigation, civilisation, and suppression of the slave trade. Yet its deeper function was to manage imperial rivalry and reduce the risk of conflict among European powers (Craven, 2012).

Effective occupation became the key legal idea. European states could not rely only on vague discovery or symbolic claims. They had to show some degree of authority, presence, administration, or control. This did not protect African sovereignty. It required European powers to make colonial claims more concrete, more administrable, and more visible to other European powers.

The conference also shows how humanitarian language could accompany imperial expansion. Anti-slavery commitments were real legal language, and the slave trade was a genuine problem. Yet that language also helped legitimate European intervention and control. The claim to suppress slavery, promote commerce, and spread civilisation made colonial administration appear as a legal and moral project.

The central argument is blunt: international law did not merely restrain empire. It helped organise the empire. It allocated claims, managed competition, defined valid occupation, protected navigation, and gave legal form to extraction and administration. Berlin was not an accident outside the discipline. It was one of the discipline’s most revealing nineteenth-century moments.

9.5 Latin American legal thought

Latin America must not appear as a passive receiver of European international law. The region produced important doctrines, arguments, and legal practices, especially around sovereignty, non-intervention, territorial integrity, recognition, debt, diplomatic protection, and resistance to foreign pressure.

Andrés Bello was one of the most important nineteenth-century Latin American jurists. His work helped adapt the law of nations to the needs of newly independent states, especially in Spanish America. Bello’s writing treated international law as a practical discipline for states seeking external recognition, territorial stability, and protection against intervention (Obregón, 2006).

The doctrine of uti possidetis also mattered. Newly independent Latin American states used inherited colonial administrative boundaries as the basis for post-independence borders. The doctrine helped reduce territorial uncertainty, even though it did not eliminate boundary disputes. Its importance later extended beyond Latin America, especially in decolonisation contexts.

Carlos Calvo’s contribution was equally significant. The Calvo Doctrine resisted the use of diplomatic protection and armed intervention by powerful states on behalf of foreign investors. It argued that foreigners should not enjoy greater rights than nationals and should seek remedies in local courts. This was a direct response to interventionist practices by European powers and the United States.

Luis María Drago developed a related argument after the Venezuela debt crisis of 1902–1903. The Drago Doctrine rejected armed force for the collection of public debts. It did not deny debt obligations, but it challenged military coercion as a tool of creditor states. The doctrine linked sovereign equality with protection against financial intervention.

Latin American legal thought, then, helped reshape international law. It defended sovereignty not as an abstract ideal, but as a practical shield against intervention, gunboat diplomacy, financial coercion, and unequal treatment. The region’s jurists contributed to a broader critique of hierarchy before the later anti-colonial turn of the twentieth century.

9.6 Humanitarian law and arbitration

The nineteenth century was not only a century of empire. It also produced major developments in humanitarian law, arbitration, and legal professionalisation. These developments did not cancel the imperial character of the period, but they show why the century cannot be reduced to colonial domination alone.

The Lieber Code of 1863, issued during the American Civil War, was an important step in codifying rules on military conduct. It addressed military necessity, prisoners, civilians, property, occupation, retaliation, and prohibited conduct. It influenced later codification of the laws of war, especially in Europe and at The Hague (Carnahan, 1998).

The 1864 Geneva Convention marked another turning point. It focused on the wounded and sick in armies in the field, and it helped institutionalise humanitarian protection through treaty law. It also reflected the growing role of organised humanitarian action, especially through the International Committee of the Red Cross.

Arbitration also gained prestige. The Alabama arbitration, concluded in 1872, resolved claims by the United States against Britain arising out of British neutrality during the American Civil War. It became a model for peaceful dispute settlement and showed that major interstate disputes could be handled through legal procedure rather than war (Moore, 1898).

The Hague movement later built on these developments. The Hague Peace Conferences of 1899 and 1907 expanded rules on arbitration, war, neutrality, and weapons. They did not abolish war, and their limits became painfully clear in 1914. Still, they strengthened the idea that law could regulate armed conflict and provide procedures for peaceful settlement.

This mixed legacy is important. The nineteenth century professionalised international law, refined legal method, expanded arbitration, and developed humanitarian restraint. It also narrowed legal membership, organised the empire, and legitimised hierarchy. The discipline became more legal, but not necessarily more equal.

10. Hague, League, and the Anti-War Turn

The early twentieth century changed the legal treatment of war. Before 1914, international law regulated war, neutrality, belligerency, and certain methods of combat, but it did not generally prohibit war as an instrument of state policy. After the First World War, the legal order moved toward institutions, collective security, permanent adjudication, and restrictions on the resort to war.

This transition was uneven. The Hague Conferences tried to legalise peace through procedure. The League of Nations tried to place war under collective discipline. The Permanent Court of International Justice strengthened adjudication. The Kellogg-Briand Pact condemned war as an instrument of national policy. None of these steps created the full Charter system, but each moved international law away from the older idea that war was a normal sovereign option.

10.1 Hague Peace Conferences

The Hague Peace Conferences of 1899 and 1907 were major efforts to regularise arbitration, codify the laws of war, and limit certain military methods. They reflected both idealism and state interest. Governments wanted mechanisms to manage disputes, but they also wanted to preserve military flexibility and strategic advantage.

The 1899 Conference created the Permanent Court of Arbitration, although it was not a permanent court in the modern sense. It provided institutional machinery, rules, and a list of potential arbitrators. The aim was to make arbitration easier, more regular, and more respectable as a method of dispute settlement.

The Hague Conventions also addressed the conduct of hostilities. They covered land warfare, neutrality, maritime warfare, bombardment, prisoners, occupation, and certain weapons. The famous Martens Clause expressed the idea that, even where treaty rules were incomplete, civilians and combatants remained under principles of humanity and the dictates of public conscience (Meron, 2000).

Yet the Hague system had clear limits. It did not abolish war. It did not create compulsory jurisdiction across the board. It did not prevent arms races, alliance politics, imperial competition, or nationalist escalation. Its legal achievement was real, but fragile. It tried to civilise war before international law had fully delegitimised war itself.

10.2 The First World War as rupture

The First World War shattered confidence in the nineteenth-century legal order. Balance-of-power politics, alliance systems, imperial rivalry, nationalism, and military planning produced a war on an enormous scale. The legal framework that had regulated neutrality, declarations of war, occupation, and conduct could not prevent catastrophe.

The war exposed a central weakness in pre-1914 international law. Law could regulate war once it began, but it lacked a strong institutional mechanism to stop states from choosing war. Arbitration existed, diplomacy existed, and Hague procedures existed, but none could control the political and military machinery that led to general war.

The war also changed the moral and legal imagination of international society. It strengthened demands for open diplomacy, collective security, minority protection, permanent adjudication, disarmament, and institutional supervision. Law had to move beyond bilateral settlement and voluntary restraint. It had to become more organised.

At the same time, the post-war settlement carried contradictions. The victors designed new institutions, but also imposed punitive and selective arrangements. Self-determination was invoked in Europe, but colonial peoples did not receive the same treatment. The language of peace advanced, while imperial structures remained.

The First World War was a rupture because it made the old system look legally inadequate. It did not immediately create a new, effective system. It forced a search for institutions that could manage peace before violence became general.

10.3 League of Nations

The League of Nations was an incomplete, but important, institutional turning point. It did not create a universal prohibition of war, and it did not remove great-power politics from international law. Yet it introduced procedures for collective security, dispute settlement, mandates, minority protection, and international administration.

The Covenant of the League required members to submit disputes to arbitration, judicial settlement, or inquiry before resorting to war. It created delay, procedure, and collective pressure. War was not fully outlawed, but it was no longer treated as an entirely free sovereign choice. The legal order began to discipline resort to force through institutional mechanisms.

The League also expanded international administration. It worked through commissions, technical bodies, mandates, and supervisory systems. Health, labour, minorities, refugees, mandates, and disarmament became subjects of organised international concern. This helped move international law beyond classical diplomacy.

Its failures were serious. The League lacked universal membership, the United States never joined, and the system depended heavily on the political will of major powers. It struggled with Japanese aggression in Manchuria, Italian aggression in Ethiopia, and the wider collapse of collective security in the 1930s.

The League’s significance lies in its institutional experiment. It failed to preserve peace, but it changed expectations about legal order. After the League, it became harder to imagine international law as only a loose system of bilateral relations among sovereigns. Institutions had become part of the legal imagination.

10.4 Mandates and colonial management

The mandate system is one of the most important examples of the League’s ambiguity. It replaced the language of direct conquest with the language of administration, development, tutelage, and international supervision. Former German and Ottoman territories were placed under the authority of mandatory powers, which were supposed to govern them on behalf of the League and for the benefit of their peoples.

The system was presented as a move away from annexation. Article 22 of the League Covenant described the well-being and development of peoples not yet able to stand by themselves under the strenuous conditions of the modern world as a sacred trust of civilisation. That language sounded protective, but it preserved hierarchy. The people concerned were not treated as equal legal actors capable of deciding their own political future.

Mandates differed in form. Some territories were considered closer to independence, while others were treated as requiring more extensive administration. This classification reflected civilisational judgement. It continued the older habit of ranking people according to perceived capacity for self-government.

The mandate system also internationalised colonial management. Mandatory powers had reporting obligations, and the Permanent Mandates Commission reviewed administration. This created oversight, but not self-determination in the later sense. The system restrained some abuses, yet it also legitimised continued external rule.

The mandate system matters because it reveals a legal transition, not a clean break. The Empire did not disappear after 1919. It was reorganised through international supervision. The vocabulary changed, but hierarchy remained.

10.5 Permanent Court of International Justice

The Permanent Court of International Justice, established after the First World War, strengthened the judicial dimension of international law. It provided a standing court for contentious cases and advisory opinions, and it helped develop legal reasoning on treaties, jurisdiction, state responsibility, minorities, international organisations, and sources of law.

The PCIJ’s importance lies partly in technique. Its judgments and advisory opinions gave international law a more disciplined legal style. The Court interpreted treaties, identified legal principles, addressed jurisdictional objections, and clarified the legal consequences of institutional acts. It helped move international law toward a more judicial vocabulary.

Advisory opinions were especially important. They allowed legal questions arising within the League system to receive authoritative treatment, even when no ordinary contentious dispute existed. This strengthened the relationship between international institutions and judicial reasoning.

The Court also contributed to the sources doctrine. The Statute of the PCIJ, later carried into the ICJ Statute with continuity in Article 38, helped organise the standard framework of treaties, custom, general principles, judicial decisions, and scholarly writings. That structure remains central to international legal education and practice.

The PCIJ did not solve the problem of consent. States still controlled much of the Court’s jurisdiction, and powerful political disputes could escape judicial settlement. Its contribution was not world government. It was a legal technique, institutional continuity, and the normalisation of international adjudication.

10.6 Kellogg-Briand Pact

The Kellogg-Briand Pact of 1928, also known as the Pact of Paris, was a major step in the legal movement against war. Its parties condemned recourse to war for the solution of international controversies, and renounced war as an instrument of national policy. This language marked a clear departure from the older idea that war was a normal sovereign tool.

The Pact did not create the full modern prohibition of force. It lacked strong enforcement machinery, it did not establish a permanent collective security organ, and it left major questions about self-defence unresolved. States could still manipulate legal language, and aggression did not vanish.

Even so, the Pact mattered. It helped delegitimise aggressive war, and it later influenced the legal treatment of crimes against peace after the Second World War. At Nuremberg, aggressive war was not presented as ordinary policy. It was treated as a punishable international crime. The Pact helped make that argument possible (Hathaway and Shapiro, 2017).

The Pact also prepared the way for the UN Charter. The Charter did not simply repeat the Pact. It went further by prohibiting the threat or use of force, preserving self-defence, and creating a collective security system through the Security Council. Still, the intellectual and legal path between the nineteenth-century regulation of war and the Charter prohibition passed through the interwar anti-war movement.

The interwar period ended in failure, but not in legal emptiness. Hague procedure, the League, mandates, the PCIJ, and the Kellogg-Briand Pact all changed international law’s structure. They did not prevent the Second World War, but they supplied institutional and doctrinal materials that shaped the post-1945 order.

11. The UN Charter Settlement

The United Nations Charter settlement was the most important institutional turning point in modern international law. It did not create a perfect legal order, and it did not remove power politics, but it changed the structure of legal argument after 1945. Sovereign equality, peaceful settlement, collective security, human rights, self-determination, and the prohibition of force moved to the centre of the legal system.

The Charter also changed the language of legitimacy. Before 1945, international law had regulated war, diplomacy, treaties, neutrality, territory, and colonial administration, but war had not been fully removed from the ordinary instruments of state policy. After 1945, states still used force, violated rights, and defended narrow interests, but they had to argue inside a legal order that treated aggression, conquest, and unilateral war as unlawful, not merely regrettable.

This was a decisive change, but not a clean moral rebirth. The Charter protected sovereign equality, yet gave special authority to five permanent members of the Security Council. It affirmed human rights, yet left enforcement heavily dependent on states. It spoke of self-determination, yet many colonial empires survived for years after 1945. The Charter order was a legal revolution with built-in political compromises.

11.1 Sovereign equality and universal membership

The Charter placed sovereign equality at the foundation of the new order. Article 2(1) states that the United Nations is based on the sovereign equality of all its members. That principle gave newly admitted states the same formal legal status as older powers, regardless of size, wealth, population, or military strength (United Nations, 1945).

Sovereign equality mattered because it changed the formal structure of membership. International law could no longer be presented openly as the law of a narrow club of “civilised” states. The language of civilisation, hierarchy, and tutelage lost much of its legitimacy, even though its effects persisted in colonialism, economic dependency, and unequal institutional power.

Universal membership also made international law more global. The United Nations became the main institutional forum in which states could debate peace, development, colonialism, human rights, economic order, and legal codification. The General Assembly, especially after decolonisation, became a place where newly independent states could challenge older legal assumptions.

Yet sovereign equality remained formal, not material. The United States, the Soviet Union, Britain, France, and China occupied a privileged position through permanent membership in the Security Council. Smaller states gained voice, membership, and legal personality, but not equal control over enforcement. This tension between formal equality and institutional hierarchy remains one of the defining features of the Charter system (Simpson, 2004).

The deeper legal point is that 1945 changed the grammar of international law. States were no longer ranked openly through civilisation as a condition of legal personality. They were formally equal members of a universal organisation, bound by common purposes and principles. That achievement was real, even though the system preserved serious inequalities.

11.2 The prohibition of force

The most important doctrinal change in the Charter was the prohibition of force. Article 2(4) requires members to refrain from the threat or use of force against the territorial integrity or political independence of any state, or in any other manner inconsistent with the purposes of the United Nations (United Nations, 1945).

This rule changed the legal status of war. Earlier international law had regulated war through rules on declarations, neutrality, occupation, reprisals, and military conduct. The Charter shifted the starting point. Force became presumptively unlawful, unless justified under a recognised exception. The two central exceptions are self-defence under Article 51 and enforcement action authorised by the Security Council under Chapter VII.

Article 51 preserves the inherent right of individual or collective self-defence if an armed attack occurs. This provision created a legal framework for defensive force, but it did not make self-defence unlimited. Necessity, proportionality, immediacy, reporting to the Security Council, and the relationship between self-defence and collective security became central issues in later doctrine and case law (Gray, 2018).

Chapter VII gives the Security Council authority to determine threats to the peace, breaches of the peace, and acts of aggression, and to decide measures needed to maintain or restore international peace and security. Those measures may include sanctions, embargoes, authorisation of force, and other collective responses. In legal design, this moved enforcement away from unilateral war and toward institutional decision-making.

The problem is practice. States have repeatedly tried to stretch self-defence, humanitarian claims, protection of nationals, counter-terrorism, and invitations by governments to justify force. The Charter did not end the war. It changed the legal burden. A state using force must now explain why its conduct falls within the Charter framework, or why another legal basis exists. That change remains one of the most important achievements of modern international law.

11.3 Collective security and veto power

The Security Council was designed as the core institution of collective security. Its basic logic is simple: threats to international peace and security should not be handled only through unilateral state action. They should be addressed through an organ empowered to make binding decisions on behalf of the international community.

That design was ambitious, but deeply political. The permanent members of the Security Council received veto power because the Charter system was built on the assumption that collective security could not function against the united opposition of the major victorious powers. The veto was the price of great-power participation. It placed geopolitical privilege inside the legal structure of the United Nations.

This arrangement created a permanent tension. On one side, the Council can authorise sanctions, peacekeeping-related mandates, international criminal tribunals, arms embargoes, and the use of force. On the other side, veto power can block action in situations involving permanent-member interests or their allies. The law of collective security is, as a result, both institutionalised and politically constrained.

The Cold War made this problem visible. Council paralysis pushed states and the General Assembly to search for other mechanisms, including peacekeeping and the Uniting for Peace procedure. After the Cold War, the Council became more active, especially in relation to Iraq, the former Yugoslavia, Rwanda, terrorism, sanctions, and peace operations. Yet selectivity remained.

The veto also affects legitimacy. When the Council acts, critics may accuse it of political selectivity. When it fails to act, critics may accuse it of institutional paralysis. This does not make the Charter system irrelevant. It shows that collective security was never separate from power. The Charter legalised great-power management while trying to restrain unilateral violence.

11.4 The ICJ and sources of law

The International Court of Justice became the principal judicial organ of the United Nations. It inherited much from the Permanent Court of International Justice, including legal method, institutional design, and the central framework for identifying sources of international law. Its Statute, annexed to the Charter, remains one of the main reference points for legal doctrine.

Article 38 of the ICJ Statute identifies the materials the Court applies: international conventions, international custom, general principles of law, and, as subsidiary means, judicial decisions and the teachings of the most highly qualified publicists. This provision became the standard teaching framework for the sources of international law (Statute of the International Court of Justice, 1945).

Treaties provide express commitments. Custom requires general practice accepted as law. General principles help fill gaps and support legal reasoning where treaty and custom are insufficient. Judicial decisions and scholarship do not create law in the same way, but they help identify, interpret, and systematise legal rules.

The ICJ also strengthened international law by giving authoritative judgments and advisory opinions on territorial disputes, use of force, diplomatic protection, immunities, self-determination, genocide, environmental obligations, maritime delimitation, and the legal consequences of occupation or unlawful situations. Its case law helped develop international law as a disciplined argumentative practice.

Yet consent still limits jurisdiction. The Court cannot hear most contentious cases unless states have accepted its jurisdiction through a special agreement, a compromissory clause, an optional clause declaration, or another recognised basis. This preserves the state-centred character of adjudication. The ICJ is powerful in legal reasoning, but limited in compulsory reach.

11.5 Human rights in the Charter order

The Charter placed human rights inside the language of international law. The preamble reaffirms faith in fundamental human rights, the dignity and worth of the human person, and the equal rights of men and women. Article 1(3) identifies international cooperation in promoting and encouraging respect for human rights and fundamental freedoms as one of the purposes of the United Nations (United Nations, 1945).

This was a major shift. Before 1945, the treatment of individuals was often treated as a matter within domestic jurisdiction, subject to limited exceptions. After 1945, the internal treatment of persons became a legitimate concern of international law. The Universal Declaration of Human Rights, the Genocide Convention, the ICCPR, the ICESCR, and later specialised human rights treaties turned that Charter language into a dense normative field.

The Charter did not immediately create strong judicial enforcement. Human rights law developed through declarations, treaties, reporting systems, treaty bodies, regional courts, special procedures, and political monitoring. States remained central to drafting, ratification, implementation, and enforcement. Yet the old claim that human rights were purely domestic became much harder to defend.

Human rights also altered sovereignty. Sovereignty still mattered, but it no longer gave states an unlimited legal shield against scrutiny. Torture, genocide, racial discrimination, apartheid, arbitrary detention, forced disappearance, and systematic persecution became matters of international legal concern. This shift transformed the relationship between state authority and individual dignity.

The Charter order, then, created a new legal vocabulary. It made human rights part of international law’s core, while leaving enforcement uneven and politically contested. That tension remains central to the modern system.

12. Decolonisation and Self-Determination

Decolonisation was one of the greatest turning points in the history of International Law. It changed the membership of the international society, the legitimacy of the empire, the meaning of sovereignty, the legal force of self-determination, and the political direction of the United Nations. The transformation was not a gift from colonial powers. It was produced through anti-colonial struggle, diplomatic pressure, legal argument, armed resistance, mass politics, and institutional change.

Before decolonisation, international law had often treated colonised peoples as objects of administration, protection, civilisation, mandate, or trusteeship. After decolonisation, many of those people became states, treaty parties, UN members, judges, diplomats, legal scholars, and makers of international law. The legal community changed because its membership changed.

The change was not only formal. Newly independent states challenged the older priorities of international law. They placed racial equality, non-intervention, development, resource sovereignty, anti-apartheid, economic justice, and self-determination at the centre of legal debate. International law became less European, less openly imperial, and more contested.

12.1 Anti-colonial legal struggle

Anti-colonial movements used law strategically. They challenged the legitimacy of colonial rule, invoked self-determination, appealed to the United Nations, demanded recognition, and exposed the contradiction between Charter principles and imperial control. Law was not the only instrument of liberation, but it became an important language of resistance.

The UN Charter gave anti-colonial claims a stronger legal setting. Article 1(2) refers to friendly relations among nations based on equal rights and self-determination of peoples. Chapters XI and XII addressed non-self-governing territories and the international trusteeship system. These provisions did not immediately end the empire, but they gave colonised peoples and supportive states a legal vocabulary to challenge it (United Nations, 1945).

Anti-colonial legal struggle also changed the meaning of sovereignty. For European powers, sovereignty had often meant control, title, jurisdiction, and imperial competence. For anti-colonial movements, sovereignty meant independence, equality, territorial integrity, political self-rule, cultural dignity, and freedom from foreign domination.

The process was uneven. Some colonies gained independence through negotiation, others through war, and others through prolonged international pressure. Some borders reproduced colonial lines. Some new states inherited weak economies, divided societies, and legal systems shaped by colonial rule. Yet the legal achievement remains fundamental: colonial rule lost its claim to legitimacy under modern international law.

Decolonisation also exposed the limits of formal equality. Newly independent states entered the UN as sovereign equals, but many remained economically dependent, militarily vulnerable, and institutionally constrained. This gap between juridical sovereignty and material power would later shape demands for a New International Economic Order.

12.2 Bandung and Third World legal agency

The Bandung Conference of 1955 was a major moment of Afro-Asian legal and political agency. It brought together newly independent and still-colonised peoples in a shared project of anti-colonial solidarity, racial equality, peaceful coexistence, economic cooperation, and resistance to domination by Cold War blocs.

Bandung should not be treated as mere diplomatic symbolism. It helped reshape the vocabulary of international law. Its principles emphasised respect for sovereignty, territorial integrity, equality of races and nations, non-intervention, non-aggression, peaceful settlement, human rights, and self-determination. These claims later appeared across UN debates, General Assembly resolutions, and Third World approaches to international law (Eslava, Fakhri and Nesiah, 2017).

The conference also challenged the assumption that legal development moved outward from Europe. Afro-Asian states and movements were not waiting to be admitted into a completed legal order. They were trying to change that order. They sought to redefine sovereignty against colonialism, neutrality against Cold War pressure, and development against inherited economic dependency.

Bandung also helped prepare the ground for the Non-Aligned Movement. Non-alignment was not simply a refusal to choose sides between superpowers. It was a legal-political claim to independent judgment, sovereign equality, and freedom from coercive alignment. It gave newly independent states a collective voice in a world still shaped by military blocs and economic hierarchy.

The legal importance of Bandung lies in agency. It shows that Third World states and movements were not passive beneficiaries of international law. They were authors, critics, and reformers of the legal order.

12.3 Resolution 1514 and colonial independence

General Assembly Resolution 1514, adopted in 1960, was a turning point in the legal history of decolonisation. The Declaration on the Granting of Independence to Colonial Countries and Peoples proclaimed that all peoples have the right to self-determination, and that colonial domination constituted a denial of fundamental human rights and an obstacle to world peace (United Nations General Assembly, 1960).

The declaration changed the legal climate. Colonialism could no longer be defended as a normal form of administration, civilisation, or tutelage. It became legally suspect, politically illegitimate, and increasingly incompatible with the Charter. Resolution 1514 helped turn self-determination from a broad political principle into a legal entitlement.

Later practice strengthened this shift. The ICJ’s advisory opinions on Namibia, Western Sahara, and the Chagos Archipelago confirmed the centrality of self-determination in the law of decolonisation. In the Chagos Advisory Opinion, the Court treated the right to self-determination as crystallised in customary international law during the period of decolonisation, and treated Resolution 1514 as a defining moment in that process (ICJ, 2019).

Resolution 1514 also rejected the delay. It stated that inadequacy of political, economic, social, or educational preparedness should never serve as a pretext for delaying independence. This directly attacked the older mandate and trusteeship logic, which had ranked people by supposed readiness for self-government.

The declaration did not solve every problem. It left difficult questions about borders, minorities, secession, internal self-determination, and post-colonial governance. Yet its basic legal effect was profound. The Empire lost the benefit of legal normality.

12.4 Permanent sovereignty over resources

Decolonisation was not only about flags, constitutions, and UN seats. Newly independent states also sought control over land, minerals, oil, forests, water, infrastructure, and development policy. Political independence without economic sovereignty looked incomplete.

General Assembly Resolution 1803 on permanent sovereignty over natural resources expressed this concern. It affirmed the right of peoples and nations to permanent sovereignty over their natural wealth and resources, and linked resource control to national development and the well-being of peoples (United Nations General Assembly, 1962).

The principle responded to a real problem. Many newly independent states inherited economies structured around extraction, foreign ownership, unequal concessions, and dependence on export commodities. Legal independence did not automatically change contracts, property relations, debt, investment structures, or market vulnerability. Resource sovereignty aimed to give states legal authority to reshape those inherited arrangements.

The principle also created tension with foreign investment law. Host states claimed authority to nationalise, regulate, and control resources. Foreign investors and capital-exporting states claimed protection against uncompensated expropriation, arbitrary treatment, and breach of acquired rights. International law became a field of struggle between sovereignty over resources and the protection of foreign property.

Permanent sovereignty over natural resources remains important because it links self-determination to economic control. It shows that decolonisation was not only a political process. It was also a demand to restructure the legal conditions of development.

12.5 New International Economic Order

The New International Economic Order, advanced in the 1970s, was an ambitious attempt to restructure international economic law. Newly independent and developing states argued that formal political equality was insufficient while trade, finance, technology, investment, and commodity markets remained unequal.

The 1974 Declaration on the Establishment of a New International Economic Order called for sovereign equality, resource sovereignty, fairer terms of trade, regulation of transnational corporations, technology transfer, development assistance, and greater participation by developing states in global economic decision-making (United Nations General Assembly, 1974).

The NIEO was legally significant because it challenged the separation between public international law and global economic structure. It argued that sovereignty required economic capacity, not merely formal independence. It also linked development, redistribution, and international cooperation to the legitimacy of the post-colonial order.

The project faced strong resistance. Industrialised states rejected many redistributive claims, defended investor protection and market access, and resisted binding duties of economic restructuring. The debt crises of the 1980s, structural adjustment, and the rise of neoliberal economic policy weakened the NIEO agenda.

Even so, the NIEO remains important. It exposed the gap between legal equality and economic inequality. It also anticipated later debates on development, global justice, debt, climate finance, technology transfer, and reform of international financial institutions. Its most important legacy may be the insistence that international law cannot be understood only through sovereignty and non-intervention. It must also be read through economic power.

12.6 Indigenous peoples and internal colonialism

Indigenous peoples complicate the state-centred model of decolonisation. Classical decolonisation focused mainly on overseas colonial territories becoming independent states. Indigenous claims often arise inside existing states, including states that are themselves post-colonial. This creates a difficult legal problem: how can international law address colonial dispossession when the colonial structure survives within recognised sovereign states?

Indigenous peoples have challenged the assumption that statehood fully resolves colonial injustice. Their claims concern land, culture, language, sacred sites, political autonomy, natural resources, consultation, free, prior, and informed consent, and historical dispossession. These claims do not always seek independent statehood. Many seek internal self-determination, legal recognition, restitution, autonomy, participation, and protection of collective identity.

The United Nations Declaration on the Rights of Indigenous Peoples, adopted in 2007, marked a major normative development. It affirms Indigenous peoples’ right to self-determination, rights to lands, territories, and resources, cultural rights, institutional autonomy, and participation in decisions affecting them (United Nations General Assembly, 2007).

ILO Convention No. 169 also remains important, especially because it is a binding treaty for its parties. It recognises Indigenous and tribal peoples’ rights to consultation, participation, land, cultural integrity, and control over their own institutions within the framework of the states in which they live (International Labour Organization, 1989).

Indigenous peoples show the limits of a purely interstate history of international law. Decolonisation changed the world map, but it did not end all colonial legal relations. Land dispossession, extractive projects, cultural destruction, and denial of collective authority continue inside many states. A serious account of self-determination must include these internal colonial questions, or it risks treating state independence as the end of the story.

13. Codification and Norm Hierarchy

After 1945, international law entered a more technical and systematic phase. The UN Charter created the institutional framework, but the daily operation of international law required more precise rules on treaties, responsibility, custom, immunities, succession, diplomatic relations, and other fields. Codification became one of the main tools for turning scattered practice, judicial reasoning, and scholarly debate into clearer legal materials.

This did not mean that international law became simple. Codification often clarified doctrine, but it also exposed disagreement. States accepted some draft articles as treaties, treated others as evidence of customary law, and resisted rules that threatened their interests. The history of codification is, for that reason, not only a story of technical legal progress. It is also a story of political negotiation, legal authority, and the struggle over who controls the content of international law.

Norm hierarchy added another layer. Classical international law was often explained through consent: states were bound because they accepted rules. After 1945, that model became harder to sustain alone. Peremptory norms, obligations owed to the international community, human rights, self-determination, and the prohibition of aggression all suggested that some legal duties could not be reduced to ordinary consent.

13.1 International Law Commission

The International Law Commission was established by the General Assembly in 1947, under Article 13 of the UN Charter, to promote the progressive development of international law and its codification. Its role became central because international law needed technical consolidation after the institutional shift of 1945.

The ILC works through special rapporteurs, reports, state comments, draft articles, draft conclusions, draft guidelines, and commentaries. This method matters. International law is not codified by academic preference alone. Draft texts pass through legal expertise, diplomatic reaction, state practice, institutional debate, and political negotiation. The Commission’s commentaries often become as important as the draft provisions themselves, because they explain the sources, reasoning, limits, and intended meaning of the text.

Its influence has been substantial. The ILC’s work contributed to the Vienna Convention on the Law of Treaties, the law of diplomatic relations, consular relations, state responsibility, diplomatic protection, the responsibility of international organisations, the identification of customary international law, and jus cogens. Not every ILC project becomes a treaty, but many shape legal argument, judicial reasoning, and state practice.

The Commission also shows the mixed nature of codification. Codification records existing law, where sufficient practice and opinio juris already exist. Progressive development goes further by proposing rules that may not yet be fully settled. The distinction is clear in theory, but often difficult in practice. Many ILC texts contain both elements, and states may disagree on which provisions reflect custom.

The ILC moved international law into a more technical age. It helped create a legal culture in which rules are debated through draft articles, commentaries, institutional reports, and state observations. This increased precision, but it also made international law more specialised. The field became less dependent on broad treatises and more dependent on technical materials produced through international institutions.

13.2 Vienna Convention on the Law of Treaties

The Vienna Convention on the Law of Treaties of 1969 is one of the most important codification treaties in modern international law. It consolidated rules on treaty formation, consent to be bound, reservations, interpretation, amendment, invalidity, termination, suspension, and the effects of treaties on third states. It is often called the “treaty on treaties”, because it regulates the legal instrument through which states create many of their obligations.

The Convention rests on pacta sunt servanda, the rule that treaties in force are binding on the parties and must be performed in good faith. This principle gives treaty law its basic stability. If states could disregard treaty commitments whenever performance became inconvenient, treaty law would lose much of its function. Good faith supports performance, interpretation, cooperation, and legal trust between parties (Vienna Convention on the Law of Treaties, 1969).

Treaty interpretation is one of the Convention’s most influential areas. Article 31 requires interpretation in good faith, according to the ordinary meaning of the terms, in their context, and in light of the treaty’s object and purpose. Article 32 allows supplementary means, including preparatory work and the circumstances of conclusion, when interpretation under Article 31 leaves ambiguity, obscurity, or manifest absurdity. This approach became central to international adjudication (Gardiner, 2015).

Reservations are another key part of the Convention. They allow states to join multilateral treaties while excluding or modifying the legal effect of certain provisions, if the reservation is permitted and compatible with the object and purpose of the treaty. This rule tries to balance universality and integrity. Too little flexibility may reduce participation. Too much flexibility may weaken the treaty’s normative content.

The Convention also deals with invalidity. Error, fraud, corruption, coercion of a representative, coercion of a state by threat or use of force, and conflict with jus cogens may affect treaty validity. These rules show that treaty consent is not always enough. Consent must be legally valid, and some agreements are unacceptable because of the circumstances in which they were made, or because of the norms they violate.

Jus cogens is the most striking example. Article 53 provides that a treaty is void if, at the time of its conclusion, it conflicts with a peremptory norm of general international law. Article 64 adds that, if a new peremptory norm emerges, any existing treaty conflicting with that norm becomes void and terminates. This introduced norm hierarchy directly into treaty law. Some rules stand above ordinary agreement, and states cannot contract out of them.

13.3 State responsibility

The Articles on Responsibility of States for Internationally Wrongful Acts, adopted by the ILC in 2001, are one of the most important doctrinal frameworks in modern international law. They do not define primary obligations, such as the duty not to use force, the duty not to commit genocide, or the duty to respect treaty commitments. They explain what happens when a state breaches an international obligation.

State responsibility is the grammar of breach. It asks whether conduct is attributable to a state, whether that conduct breaches an international obligation, whether any circumstance precludes wrongfulness, and what legal consequences follow. Without this framework, international law would have rights and duties, but no coherent structure for responsibility.

Attribution is central. A state acts through organs, officials, entities exercising governmental authority, and, in some circumstances, persons or groups acting under its direction or control. This matters because states often act through military forces, police, regulators, public corporations, local authorities, intelligence services, and proxy actors. Attribution decides when conduct becomes the conduct of the state (International Law Commission, 2001).

Breach is the next step. A breach occurs when conduct is not in conformity with what an international obligation requires. The content of the obligation comes from primary law: a treaty, custom, general principle, or another source. The responsibility framework does not ask whether the obligation is wise. It asks whether the state failed to comply.

The Articles also recognise circumstances precluding wrongfulness, including consent, self-defence, countermeasures, force majeure, distress, and necessity. These are not excuses of convenience. They operate under strict conditions because they allow conduct that would otherwise be wrongful. Necessity, for example, cannot be used loosely to escape legal obligations whenever a state faces difficulty.

The consequences of responsibility include cessation, assurances, and guarantees of non-repetition, and reparation. Reparation may take the form of restitution, compensation, and satisfaction. The basic principle, reflected in the Chorzów Factory case, is that reparation should wipe out, as far as possible, the consequences of the wrongful act (Permanent Court of International Justice, 1928).

Countermeasures are also important. They allow an injured state, under strict conditions, to take non-forcible measures that would otherwise be unlawful, in order to induce compliance by the responsible state. This gives international law a decentralised enforcement mechanism, but one that remains legally constrained.

The most significant development lies in obligations owed beyond one injured state. The Articles recognise that some obligations are owed to a group of states, or to the international community as a whole. This links state responsibility to erga omnes obligations, jus cogens, and the protection of common legal interests.

13.4 Jus cogens and erga omnes

The rise of jus cogens and erga omnes obligations challenged a purely consent-based model of international law. Classical doctrine often treated states as bound because they consented through treaty, custom, or accepted practice. Peremptory norms and community obligations suggest a different idea: some rules protect fundamental interests of the international community, and states cannot avoid them through ordinary consent.

Jus cogens refers to peremptory norms of general international law. These are norms accepted and recognised by the international community of states as a whole as norms from which no derogation is permitted. The usual examples include the prohibitions of aggression, genocide, slavery, racial discrimination, apartheid, torture, and basic rules of international humanitarian law, although the precise list and consequences continue to generate debate (International Law Commission, 2022).

The legal effect of jus cogens is strongest in treaty law. A treaty conflicting with a peremptory norm is void. Yet the concept also affects state responsibility, recognition, cooperation, immunity debates, and the legal consequences of serious breaches. Jus cogens tells states that some legal interests are not available for bargaining.

Erga omnes obligations are related, but distinct. In the Barcelona Traction case, the ICJ explained that some obligations are owed to the international community as a whole, and that all states have a legal interest in their protection (International Court of Justice, 1970). This does not necessarily mean that every erga omnes obligation is jus cogens, or that every procedural consequence is automatic. The key point is that the obligation is not owed only to one injured state.

Self-determination, the prohibition of genocide, and fundamental human rights have been treated as obligations with a community dimension. This changed international law’s structure. If some obligations are owed to all, then breach is not merely a bilateral matter between wrongdoer and injured state. It concerns the legal order more broadly.

The challenge is enforcement. Jus cogens and erga omnes language can be powerful, but practical consequences depend on courts, institutions, state reactions, sanctions, domestic implementation, and political will. The concepts strengthen norm hierarchy, but they do not remove the decentralised character of international law.

13.5 Customary law and evidence

Customary international law became more methodologically demanding after 1945. In older accounts, custom was often described broadly as general practice accepted as law. Modern practice requires more careful analysis. Lawyers must identify state practice, assess whether it is sufficiently general, representative, and consistent, and then determine whether states acted out of a sense of legal obligation, known as opinio juris.

The ILC’s Conclusions on Identification of Customary International Law, adopted in 2018, confirmed the two-element approach: general practice and acceptance as law. This matters because custom can bind states even without treaty ratification. It must not be identified casually, especially in a world of nearly universal state membership, regional diversity, and political disagreement (International Law Commission, 2018).

State practice may include diplomatic acts, official statements, military manuals, domestic legislation, national court decisions, treaty practice, votes in international organisations, pleadings before courts, and conduct in international relations. Not every act has the same value. Practice must be assessed in context, and silence may matter only when a reaction would be expected.

Opinio juris is often harder to prove. States may act for political convenience, habit, morality, courtesy, fear, strategy, or legal duty. Custom requires evidence that states accept the practice as legally required, permitted, or prohibited. This makes legal reasoning more demanding, because the same conduct may have several explanations.

General Assembly resolutions can contribute to customary law, but they do not automatically create it. Their legal value depends on content, voting patterns, explanations of the vote, repetition, state practice, and whether states treat the principle as legally binding. Resolution 1514 on decolonisation, for example, gained major legal importance because it was linked to wider practice and opinio juris on self-determination.

The difficulty is universal custom in a divided world. Newly independent states, powerful states, regional groups, and affected communities may disagree on the content of custom. A method that relies only on powerful-state practice risks reproducing hierarchy. A method that treats broad political aspiration as law too quickly risks weakening legal discipline. Customary law, for that reason, remains one of the most contested sources of international law.

14. Individuals, Rights, and Crimes

Modern international law no longer treats the state as the only legally relevant actor. States remain central, but individuals now hold rights, bear certain obligations, appear before international bodies, submit complaints in some systems, receive protection as refugees, and face direct criminal responsibility for international crimes. This shift changed the structure of the discipline.

The change did not happen in one moment. It developed through abolitionism, minority protection, labour law, humanitarian law, refugee law, human rights law, the Nuremberg and Tokyo trials, the Genocide Convention, the Geneva Conventions, regional courts, ad hoc tribunals, and the International Criminal Court. The individual entered international law through several doors, not only through human rights.

This development also changed sovereignty. A state’s treatment of persons under its authority could no longer be described as purely internal. Torture, genocide, forced labour, racial discrimination, arbitrary detention, persecution, and war crimes became matters of international legal concern.

14.1 The individual as legal subject

Classical international law was often described as a law between states. Individuals appeared mainly through nationality, diplomatic protection, alien treatment, piracy, slavery, and certain wartime rules. They were affected by international law, but they rarely held rights or duties directly at the international level.

That model changed gradually. International labour law recognised that working conditions could be matters of international concern. Refugee law protected persons who could no longer rely on their state of nationality. Humanitarian law protected wounded soldiers, prisoners of war, civilians, and persons under occupation. Human rights law recognised rights held by individuals against states.

The individual also gained direct obligations. International criminal law made it clear that a state's office does not automatically shield individuals from responsibility for certain crimes. A commander, minister, soldier, official, militia leader, or head of state may incur criminal responsibility for conduct prohibited by international law.

This does not mean that individuals became equal to states in the international legal system. They cannot usually make treaties, create customs, or control international institutions. Their access to enforcement mechanisms remains uneven. Yet the conceptual shift is decisive. Individuals are no longer merely objects of international protection. They are, in specific fields, subjects of international law.

This development also fragmented the old sovereignty model. A state may still claim domestic jurisdiction, but it cannot use that claim to silence all external legal scrutiny. Human rights bodies, international criminal courts, refugee institutions, treaty committees, and regional courts all limit the idea that the state is the exclusive judge of its internal affairs.

14.2 Nuremberg and Tokyo

The Nuremberg and Tokyo trials were major doctrinal breaks because they imposed international criminal responsibility directly on individuals. The defendants were not treated merely as agents of states whose conduct could only produce state responsibility. They were prosecuted as persons answerable under international law.

The Nuremberg Charter recognised crimes against peace, war crimes, and crimes against humanity. The judgment rejected the argument that international law only binds states. It stated that crimes against international law are committed by men, not abstract entities, and that only by punishing individuals can international law be enforced in such cases (International Military Tribunal, 1946).

Crimes against peace were especially significant. Aggressive war was treated not only as an unlawful act of state, but as a crime for which leaders could be held responsible. This was built on interwar developments, including the Kellogg-Briand Pact, but gave them a sharper criminal consequence.

War crimes had older roots in the laws and customs of war. Nuremberg and Tokyo applied these rules to military and civilian leaders involved in unlawful conduct during armed conflict. Crimes against humanity expanded the legal focus by addressing atrocities committed against civilian populations, including acts linked to persecution and mass violence.

The trials also raised legal concerns. Critics argued that some charges, especially crimes against peace and crimes against humanity, involved retroactive punishment. Defenders argued that the defendants’ conduct violated existing international obligations and fundamental legal principles. This debate remains part of Nuremberg’s legacy.

The greatest contribution of Nuremberg and Tokyo was the principle that official position does not erase criminal responsibility. International law could reach individuals, including leaders, when the crimes were grave enough. Later tribunals and the ICC developed that principle further.

14.3 Genocide and humanitarian law

The Genocide Convention of 1948 and the Geneva Conventions of 1949 gave post-war international law a stronger protective structure. They responded to mass atrocity, occupation, prisoner abuse, civilian suffering, and the failures of earlier legal regimes. They also made clear that certain forms of violence are matters of international concern, even when committed by state authorities.

The Genocide Convention defines genocide as certain acts committed with the intent to destroy, in whole or in part, a national, ethnic, racial, or religious group, as such. The protected groups are limited, and the special intent requirement is demanding. This makes genocide difficult to prove, but it also marks it as a distinct crime focused on group destruction (Convention on the Prevention and Punishment of the Crime of Genocide, 1948).

The 1949 Geneva Conventions codified protections for wounded and sick armed forces, shipwrecked members of armed forces at sea, prisoners of war, and civilians. Common Article 3, applicable in non-international armed conflicts, became one of the most important provisions in humanitarian law. It requires humane treatment and prohibits violence to life and person, hostage-taking, humiliating and degrading treatment, and sentences without proper judicial guarantees (Geneva Conventions, 1949).

Occupation law is also central. The Fourth Geneva Convention regulates the protection of civilians in occupied territory. It limits deportations, collective punishment, unlawful transfers, and abuse of protected persons. Occupation does not transfer sovereignty to the occupying power. It creates temporary authority, constrained by humanitarian obligations.

Grave breaches provisions created obligations to search for and prosecute, or extradite, persons accused of particularly serious violations. This strengthened the connection between humanitarian law and criminal accountability. It also helped develop the idea that some crimes concern all states.

The separation between jus ad bellum and jus in bello is crucial. A state may use force unlawfully, but all parties still remain bound by humanitarian law. A state acting in lawful self-defence must still respect civilian protection, proportionality, distinction, humane treatment, and limits on methods and means of warfare. This separation protects victims by preventing humanitarian duties from depending on which side has the better legal claim to war.

14.4 Human rights treaty systems

Human rights treaty systems changed the relationship between state sovereignty and the domestic treatment of individuals. The Universal Declaration of Human Rights supplied a common normative vocabulary. The ICCPR and ICESCR later transformed many of those principles into treaty obligations. Regional systems in Europe, the Americas, and Africa created additional layers of protection, including courts and commissions.

The ICCPR protects civil and political rights, including life, liberty, fair trial, expression, religion, privacy, political participation, and freedom from torture or arbitrary detention. The ICESCR protects economic, social, and cultural rights, including work, health, education, social security, adequate living conditions, and participation in cultural life. The two Covenants show that human dignity cannot be reduced to one category of rights (International Covenant on Civil and Political Rights, 1966; International Covenant on Economic, Social and Cultural Rights, 1966).

Monitoring bodies made human rights law more institutional. Treaty committees examine state reports, issue general comments, and, under some procedures, consider individual communications. Their views may not operate like judgments of a domestic supreme court, but they influence interpretation, state practice, advocacy, and legal development.

Regional courts added stronger adjudication in some parts of the world. The European Court of Human Rights, the Inter-American Court of Human Rights, and the African human rights system have all developed case law on state obligations, remedies, due diligence, discrimination, detention, political rights, social rights, Indigenous rights, and transitional justice.

Human rights law changed sovereignty by making internal conduct externally reviewable. A state can no longer say, with the same authority as before 1945, that its treatment of persons under its jurisdiction is solely a domestic matter. Ratified treaties, customary norms, peremptory prohibitions, and institutional procedures all limit that claim.

The limits remain real. Enforcement is uneven, reservations may weaken obligations, some states resist external review, and political selectivity affects human rights practice. Yet the doctrinal change is profound. International law now speaks directly to how states treat persons, not only to how states treat each other.

14.5 International criminal courts

The creation of international criminal courts after the Cold War marked another major turning point. The International Criminal Tribunal for the former Yugoslavia and the International Criminal Tribunal for Rwanda revived international criminal adjudication after decades of limited institutional development. They showed that international courts could prosecute genocide, crimes against humanity, war crimes, and serious violations of humanitarian law.

The ICTY developed important jurisprudence on individual criminal responsibility, command responsibility, joint criminal enterprise, sexual violence, ethnic cleansing, and the classification of armed conflicts. The ICTR made major contributions to the law of genocide, including recognition that rape and sexual violence could constitute acts of genocide when committed with the required intent (International Criminal Tribunal for Rwanda, 1998).

Hybrid and internationalised tribunals added further models. Courts for Sierra Leone, Cambodia, Lebanon, Kosovo, and other contexts combined domestic and international elements in different ways. These institutions responded to the practical difficulty of building accountability systems that were both legally credible and connected to affected societies.

The International Criminal Court, created by the Rome Statute of 1998, established the first permanent international criminal court with jurisdiction over genocide, crimes against humanity, war crimes, and the crime of aggression, subject to jurisdictional limits. Its creation reflected the ambition to move beyond ad hoc justice and create a standing institution (Rome Statute of the International Criminal Court, 1998).

The ICC remains contested. It depends heavily on state cooperation for arrests, evidence, enforcement of sentences, and access to territory. It has faced accusations of selectivity, especially in its early focus on African situations, although its docket has since widened. Powerful non-party states can remain outside its ordinary treaty jurisdiction, except in limited circumstances involving Security Council referrals or territorial jurisdiction.

International criminal law is a turning point, but not a complete solution. It individualises responsibility for mass violence, yet it cannot substitute for prevention, political settlement, reparations, institutional reform, or state responsibility. Its importance lies in the legal principle that some crimes are so serious that individuals may be answerable before international courts, even when national systems fail or refuse to act.

15. Economic Globalisation and Legal Power

Economic globalisation changed international law by moving finance, trade, debt, investment, development, and corporate conduct closer to the centre of the discipline. International law was no longer only about war, diplomacy, borders, treaties, and state responsibility. It became a legal architecture for markets, capital movement, institutional lending, development policy, trade liberalisation, and investor protection.

This shift matters because economic law often works through technical language. Terms such as conditionality, non-discrimination, market access, expropriation, fair and equitable treatment, debt sustainability, and regulatory coherence may sound neutral. In practice, they shape what states can regulate, how they can tax, what they can nationalise, how they can protect public services, and how much policy space they retain.

The central tension is clear. International economic law can stabilise cooperation, reduce discrimination, protect investment, and create dispute settlement mechanisms. It can also strengthen inequality, limit domestic policy choices, protect private economic power, and make formal sovereign equality look much stronger than it is in material terms.

15.1 Bretton Woods institutions

The Bretton Woods institutions, created in the aftermath of the Second World War, placed finance and development inside a permanent international legal framework. The International Monetary Fund was designed to promote monetary cooperation, exchange stability, and balance-of-payments support. The World Bank, initially the International Bank for Reconstruction and Development, focused first on reconstruction, then increasingly on development lending.

These institutions changed the history of international law because they made economic management an institutionalised legal concern. International law now governs lending, repayment, currency stability, development projects, financial surveillance, technical assistance, and economic adjustment. The field expanded well beyond the older focus on treaties, diplomatic relations, and war.

The IMF and World Bank are treaty-based institutions, with legal personality, voting rules, institutional mandates, and internal decision-making procedures. They are not ordinary charities, commercial banks, or political clubs. They operate through legal instruments, loan agreements, policy conditions, institutional rules, and formal relations with member states.

Their influence, however, has always exceeded ordinary legal form. A loan condition can affect taxation, public employment, subsidies, privatisation, exchange policy, social spending, and regulatory reform. A development project can reshape land use, infrastructure, environmental protection, Indigenous communities, and public administration. For that reason, Bretton Woods law is not merely financial law. It is also a law about state capacity.

The main legal issue is policy space. States formally consent to membership and loan arrangements, but economic vulnerability can make consent less meaningful. A state facing a debt crisis, currency collapse, or fiscal emergency may accept conditions that reshape its domestic order. This does not make every condition unlawful, but it shows why economic law must be analysed through power, not only through consent.

15.2 GATT and WTO law

The General Agreement on Tariffs and Trade, adopted in 1947, created a legal framework for reducing tariffs, limiting discriminatory trade barriers, and stabilising post-war commercial relations. It was initially provisional and institutionally modest, but it became the foundation of the modern trade regime.

The World Trade Organization, created in 1995, transformed that framework into a stronger institution. It brought goods, services, intellectual property, and dispute settlement into a more integrated system. The move from GATT to the WTO marked a major legal shift, because trade law became more judicialised, more detailed, and more enforceable.

The core principles are non-discrimination, most-favoured-nation treatment, and national treatment. Most-favoured-nation treatment requires a state to extend trade advantages granted to one member to other members, unless a recognised exception applies. National treatment requires imported products, once inside the market, to be treated no less favourably than like domestic products. These principles aim to prevent protectionism and unequal commercial treatment.

The WTO dispute settlement system also changed trade law. It gave members a structured procedure for claims, panels, appellate review, compliance, and authorised retaliation. This made trade law one of the most legalised areas of international law. States could challenge each other through legal argument, rather than relying only on diplomacy or commercial pressure.

The system also generated development tensions. Many developing states argued that trade liberalisation could constrain industrial policy, food security, public health, technology access, and economic diversification. The Agreement on Trade-Related Aspects of Intellectual Property Rights became especially controversial because it linked trade law to patents, medicines, seeds, technology, and knowledge governance.

WTO law shows how legal equality and economic inequality can coexist. Every member is formally part of the same system, but not every member has the same bargaining power, litigation capacity, export profile, or resilience against retaliation. Trade law disciplines protectionism, but it also reflects the structure of the global economy in which states compete from unequal positions.

15.3 Investment law and arbitration

International investment law expanded rapidly through bilateral investment treaties, investment chapters in trade agreements, and investor-state dispute settlement. Its basic promise was to protect foreign investors against certain forms of state conduct, including uncompensated expropriation, discriminatory treatment, denial of justice, and breach of fair and equitable treatment.

The doctrinal shift was significant. Traditionally, international law treated states as the main parties to international claims. Foreign investors depended on diplomatic protection by their home state, or on domestic courts in the host state. Investment treaties changed this arrangement by allowing private investors to bring claims directly against host states before international arbitral tribunals.

This made private investors powerful users of international legal mechanisms. A corporation could challenge state measures affecting licences, taxes, mining concessions, public utilities, environmental regulation, emergency measures, or regulatory reform. States remained the formal treaty-makers, but investors became direct beneficiaries and claimants under those treaties.

Investor-state arbitration altered the balance between public authority and private rights. It gave investors protection against abusive state conduct, which can be important in contexts of expropriation, corruption, politicised courts, or arbitrary treatment. It also created concern that legitimate public regulation could be challenged as a treaty breach, especially when awards involved large compensation claims.

The debate over regulatory space became central. States need room to protect public health, labour rights, the environment, Indigenous lands, financial stability, and public services. Investment law must decide when regulation becomes unlawful interference with protected investment, and when it remains a valid exercise of sovereign authority.

Investment law also shows how international law can empower non-state actors without fully democratising the legal order. Investors gained strong procedural rights. Affected communities, workers, consumers, and Indigenous peoples often had weaker access to the same arbitral process, even when disputes concerned their land, water, labour conditions, or environment.

15.4 Debt and conditionality

Debt is one of the clearest examples of how formal sovereign equality can coexist with deep material inequality. A debtor state and a creditor state may be equal in legal personality, but their bargaining positions may be radically different. The same is true when a state negotiates with international financial institutions, private bondholders, rating agencies, or creditor committees.

International law affects debt through loan agreements, sovereign bonds, institutional rules, restructuring mechanisms, domestic court litigation, investment arbitration, and financial conditionality. Debt law may appear technical, but it can determine the level of social spending, public investment, taxation, public-sector employment, and access to essential services.

Conditionality is especially important. Financial assistance may be linked to fiscal consolidation, privatisation, subsidy removal, currency reform, pension changes, trade liberalisation, or institutional restructuring. Some conditions may be defensible as measures to restore stability. Others may shift social costs onto vulnerable populations, weaken public services, or narrow democratic policy choices.

The legal problem is not simply whether a state consented. Consent under financial distress is still legally relevant, but it must be understood in context. A state facing default, currency crisis, or exclusion from credit markets may have little realistic choice. This exposes the limits of a purely formal account of sovereignty.

Debt also affects self-determination and development. A state may be politically independent, yet unable to pursue development policy because of debt service, market pressure, or external conditions. In this area, international law does not merely regulate obligations. It shapes the practical capacity of states to govern.

The history of international economic law, for that reason, must be read alongside the history of decolonisation. Newly independent states gained legal personality, but many entered a global economy structured by inherited dependency, commodity vulnerability, foreign debt, and unequal access to capital. Debt law became one of the places where post-colonial sovereignty met economic constraint.

15.5 Corporations and private authority

Corporations have become central actors in global governance. They control supply chains, digital infrastructure, extractive projects, pharmaceuticals, finance, logistics, food systems, private security, data flows, and technology platforms. They do not have the same legal status as states, but they can exercise power across borders on a scale that international law can no longer ignore.

Corporate authority appears in several forms. Multinational enterprises can influence treaty negotiations, shape private standards, bring investment claims, structure global production, shift profits across jurisdictions, and affect labour, land, environment, privacy, and public health. In some sectors, corporate standards may influence behaviour more quickly than treaties.

Business and human rights law emerged because classical international law did not adequately address corporate impact. The UN Guiding Principles on Business and Human Rights rest on three pillars: the state duty to protect human rights, the corporate responsibility to respect human rights, and access to remedies for victims. They are not a binding treaty, but they have become a major reference point for legislation, due diligence, litigation, and corporate compliance (United Nations Human Rights Council, 2011).

Supply chains create special accountability problems. A company headquartered in one state may rely on suppliers, subcontractors, security providers, or extraction sites in several others. Harm may occur far from the parent company, and victims may face barriers in local courts. This makes jurisdiction, parent-company liability, due diligence, disclosure, and remedy central legal issues.

Corporations also operate within investment law. A company may challenge regulation through investor-state arbitration, while communities affected by the same investment may lack equivalent international standing. This asymmetry is one of the most serious legitimacy problems in international economic law.

Private authority does not replace the state, but it changes the field. States still make treaties, regulate markets, and create legal personality. Yet corporations shape norms, enforce standards, move capital, and influence legal outcomes. The history of international law, if it remains only state-centred, cannot explain this form of power.

16. Environment, Commons, and Shared Risks

Environmental law became a major turning point because it changed the temporal and material focus of international law. Classical international law often dealt with borders, war, diplomacy, trade, and responsibility after injury. Environmental law required a different logic: prevention, cooperation, scientific uncertainty, risk management, due diligence, and protection of shared ecological systems.

This shift challenged older ideas of sovereignty. A state may control territory, but pollution, climate change, biodiversity loss, ocean degradation, and atmospheric harm do not respect borders. Environmental law forced international law to ask how far domestic activities can be regulated when their effects spread across frontiers, across generations, and across global commons.

The field also exposed a deep distributive tension. Industrialised states contributed heavily to environmental degradation, while many developing states faced pressure to protect the environment without sacrificing development. That tension shaped sustainable development, common but differentiated responsibilities, climate finance, technology transfer, and debates over loss and damage.

16.1 International environmental law

International environmental law developed around prevention, cooperation, and harm beyond borders. One of its basic principles is that states have sovereignty over their natural resources, but also a responsibility to ensure that activities within their jurisdiction or control do not cause significant damage to the environment of other states or areas beyond national jurisdiction. This principle appeared in the Stockholm Declaration and later in the Rio Declaration (United Nations Conference on the Human Environment, 1972; United Nations Conference on Environment and Development, 1992).

The preventive logic is central. Environmental harm is often difficult, expensive, or impossible to reverse. Once a species disappears, a coral reef collapses, a toxic spill contaminates groundwater, or greenhouse gases accumulate in the atmosphere, later compensation may be inadequate. Environmental law, as a result, places weight on due diligence, prior assessment, notification, consultation, monitoring, and cooperation.

Scientific uncertainty also changed the legal method. States and courts had to deal with risk before full certainty existed. The precautionary approach was developed because waiting for complete proof may permit serious or irreversible harm. This does not mean every uncertain risk automatically prohibits activity. It means uncertainty becomes part of legal decision-making, rather than an excuse for inaction.

Environmental impact assessment became one of the most important tools of environmental governance. It requires states to study possible environmental consequences before approving activities that may cause significant harm. The ICJ has recognised environmental impact assessment as a requirement under general international law where there is a risk of significant transboundary harm (International Court of Justice, 2010).

International environmental law also changed state responsibility. Harm may be cumulative, diffuse, scientifically complex, and caused by many public and private actors. This makes attribution, causation, reparation, and prevention more difficult than in a simple bilateral injury. Environmental law often works less through after-the-fact compensation, and more through procedural duties, cooperation, and regulatory standards.

16.2 Stockholm, Rio, and sustainable development

The 1972 Stockholm Conference marked the beginning of modern international environmental law as a visible field. It placed environmental protection on the international agenda, connected environmental harm with human welfare, and produced principles that shaped later treaty-making and institutional development.

The 1992 Rio Conference expanded the field. It linked environment and development, produced the Rio Declaration, Agenda 21, the climate and biodiversity conventions, and strengthened the language of sustainable development. Rio made clear that environmental protection could not be separated from poverty, technology, consumption, finance, and development priorities.

Sustainable development became the central compromise. It recognises that states need economic development, especially where poverty, inequality, and infrastructure gaps remain severe. It also recognises that development cannot be pursued by destroying ecological systems needed for human survival and future generations. The concept is useful because it connects economic and environmental concerns. It is also contested because it can be invoked to support very different policies.

The precautionary approach, public participation, access to information, environmental impact assessment, and common but differentiated responsibilities all gained importance through this period. These principles helped move environmental law away from narrow bilateral harm and toward broader governance of shared risks.

Common but differentiated responsibilities became especially important. It recognises that all states share responsibility for environmental protection, but not all states have contributed equally to harm, and not all have the same capacity to respond. This principle became central to climate law, biodiversity debates, and development finance.

Stockholm and Rio show the basic tension of environmental law. Developing states resisted environmental obligations that would freeze global inequality or restrict their development. Industrialised states accepted environmental cooperation, but often resisted strong redistributive duties. The law that emerged was ambitious in principle, but uneven in enforcement.

16.3 Law of the sea and common heritage

The United Nations Convention on the Law of the Sea is one of the most comprehensive codification projects in international law. It organises maritime space into legal zones, including internal waters, territorial sea, contiguous zone, exclusive economic zone, continental shelf, high seas, and the Area, which covers the deep seabed beyond national jurisdiction.

UNCLOS balances coastal authority and common use. Coastal states have sovereignty in the territorial sea, sovereign rights over resources in the exclusive economic zone, and rights over the continental shelf. Other states retain freedoms of navigation, overflight, laying submarine cables, and other lawful uses. The Convention does not treat the ocean as one uniform space. It divides legal authority according to zone, function, and interest (United Nations Convention on the Law of the Sea, 1982).

The exclusive economic zone was a major innovation. It gave coastal states rights over living and non-living resources up to 200 nautical miles, while preserving important navigational freedoms for other states. This compromise responded to demands by coastal and developing states for greater control over nearby resources, without fully territorialising the ocean.

The common heritage of mankind applies to the deep seabed Area and its resources. This concept challenged pure appropriation. It treated seabed minerals beyond national jurisdiction as resources to be managed for the benefit of humankind as a whole, with special attention to developing states. The International Seabed Authority was created to organise and control activities in the Area.

UNCLOS also strengthened dispute settlement. The International Tribunal for the Law of the Sea, arbitral tribunals, and other procedures provide mechanisms for resolving maritime disputes. This has made the law of the sea one of the more judicialised areas of international law, especially in maritime delimitation, prompt release, fisheries, and marine environmental protection.

The law of the sea matters historically because it connects old maritime debates with modern concerns. Freedom of the seas, coastal security, resource control, navigation, marine science, environmental protection, and common heritage all meet inside one legal framework. It is one of the clearest examples of international law managing shared space.

16.4 Climate change law

Climate change law exposes the limits of consent-based cooperation when harm is global, cumulative, scientifically complex, and urgent. Greenhouse gas emissions come from many states, sectors, corporations, and historical periods. Their effects fall unevenly, often most severely on states and communities that contributed least to the problem.

The UN Framework Convention on Climate Change created the basic legal architecture. It recognised the climate system as a common concern of humankind, and placed common but differentiated responsibilities at the centre of cooperation. The Kyoto Protocol later imposed quantified emissions commitments on developed states. The Paris Agreement shifted the structure toward nationally determined contributions, reporting, progression, transparency, and a long-term temperature goal (United Nations Framework Convention on Climate Change, 1992; Paris Agreement, 2015).

The Paris model is politically flexible, but legally difficult. Nationally determined contributions allow broad participation, because states choose their own commitments. Yet that flexibility weakens direct enforcement. The system relies heavily on transparency, peer pressure, domestic implementation, scientific assessment, finance, and repeated strengthening of commitments.

Loss and damage have become central because mitigation and adaptation are not enough for many vulnerable states. Sea-level rise, extreme weather, desertification, displacement, ocean warming, and irreversible ecological harm raise questions of responsibility, finance, remedy, and survival. Small island states have been especially important in pushing climate law toward accountability.

Climate litigation has also become more important. Domestic courts, regional human rights bodies, the International Tribunal for the Law of the Sea, and the International Court of Justice have been asked to clarify duties linked to emissions, human rights, marine protection, intergenerational equity, and state responsibility. Recent advisory opinions have strengthened the idea that existing international law already contains legal duties relevant to climate protection (International Tribunal for the Law of the Sea, 2024; International Court of Justice, 2025).

The doctrinal challenge is enforcement. Climate law has legal obligations, but no global legislature, no global environmental police, and no simple court-centred enforcement model. Its success depends on national regulation, international cooperation, finance, technology, corporate accountability, scientific monitoring, and political pressure. This makes climate change one of the hardest tests of international law’s capacity to govern shared risk.

16.5 Space, cyber, and new domains

Space, cyber operations, artificial intelligence, and other technological fields test older legal categories. The basic doctrines remain familiar: sovereignty, jurisdiction, due diligence, attribution, responsibility, peaceful use, non-intervention, use of force, and cooperation. The difficulty lies in applying them to domains that are technically complex, fast-moving, and often shaped by private actors.

Outer space law developed through the principle that outer space is not subject to national appropriation, and that exploration and use must be carried out for the benefit and interests of all countries. The Outer Space Treaty established peaceful-use principles, responsibility for national activities, liability for damage, and registration-related duties. Yet new commercial activity, satellite dependence, space debris, military uses, and resource extraction have created pressures that older treaty rules did not fully anticipate (Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, 1967).

Cyber operations raise similar problems. A cyber operation may affect elections, hospitals, banks, energy grids, military systems, or private data, without crossing borders in a physical way. International lawyers must ask when such conduct violates sovereignty, amounts to intervention, triggers state responsibility, or reaches the threshold of use of force or armed attack.

Attribution is especially difficult. States may act through intelligence services, military cyber units, proxies, criminal groups, contractors, or loosely connected actors. Technical attribution and legal attribution are not the same. A state may identify the source of malware, but still needs legal evidence connecting conduct to another state under the rules of responsibility.

Private actors are also central. Technology companies, satellite operators, cloud providers, cybersecurity firms, platform companies, and artificial intelligence developers shape the practical environment in which states act. Public international law still focuses heavily on states, but new domains show how state power and private infrastructure now operate together.

These fields do not require abandoning old doctrines. They require disciplined adaptation. The history of international law shows that new domains repeatedly force old categories to stretch. The sea, airspace, outer space, cyberspace, and the climate system all raise the same basic question: can international law govern shared risks before power and technology outrun legal control?

Also read

• International Law and Colonialism

• Treaty of Westphalia 1648

• The Age of Grotius: Foundations and Impact on International Law

• The Nineteenth Century's Impact on Modern International Law

• Principle of Sovereign Equality of States

• Principle of Self-Determination of Peoples

• The Vienna Convention on the Law of Treaties

• State Responsibility in International Law

17. Historiography and Critical Schools

The final turning point is historiographical. International law changed not only because new treaties, courts, institutions, and doctrines appeared, but also because scholars began to challenge the discipline’s own memory. The way international law tells its past affects how it understands sovereignty, empire, human rights, development, war, trade, and global governance.

Classical histories often presented international law as a European discipline that gradually became universal. Critical histories questioned that narrative. They asked whose experience had been treated as universal, whose violence had been normalised, whose legal thought had been ignored, and whose political interests had been protected by supposedly neutral doctrine.

This matters because legal history is never only about the past. States, courts, institutions, and scholars use historical narratives to legitimise present claims. A serious reader must ask what each version of the past includes, what it excludes, and who benefits when one history becomes authoritative.

17.1 Third World Approaches

Third World Approaches to International Law, usually called TWAIL, became one of the most important historiographical movements in modern international legal scholarship. TWAIL does not treat colonialism as a side issue. It argues that empire, racial hierarchy, economic dependency, intervention, development policy, and unequal trade were central to the formation of international law (Anghie, 2005; Chimni, 2006).

TWAIL challenged the comforting view that international law was originally a European law of equal states, later distorted by colonial abuse. Its claim is sharper. International law helped create, justify, administer, and reform imperial relations. Doctrines of sovereignty, recognition, civilisation, trusteeship, mandate, development, intervention, and economic governance all carried traces of hierarchy.

This approach also recovers Third World agency. Colonised peoples, newly independent states, Afro-Asian movements, Latin American jurists, anti-apartheid campaigners, and development coalitions did not merely receive international law. They used it, criticised it, reshaped it, and exposed its contradictions. Decolonisation, Bandung, the Non-Aligned Movement, permanent sovereignty over natural resources, and the New International Economic Order all show legal agency by states and peoples resisting domination.

TWAIL is not a rejection of all international law. It is a critique of how international law has often operated. Many TWAIL scholars recognise that the same discipline can provide tools against empire, racial domination, economic dependency, and intervention. The problem is that those tools are unstable. The language of sovereignty can protect weaker states, but it can also protect abusive governments. Human rights can defend individuals, but they can also support selective intervention. Development can support welfare, but it can also discipline post-colonial economies.

TWAIL’s contribution to the history of International Law is, for that reason, methodological and political. It forces readers to study the legal order through hierarchy, not only through equality; through empire, not only through diplomacy; through resistance, not only through institutions.

17.2 Feminist legal histories

Feminist legal histories challenge the male subject of classical international law. Traditional accounts focused on statesmen, diplomats, soldiers, jurists, sovereigns, merchants, and judges, while women appeared rarely, often as victims, symbols, or humanitarian objects. Feminist scholarship asks how international law was shaped by gendered assumptions about authority, violence, labour, family, nationality, public power, and private life (Charlesworth and Chinkin, 2000).

One major issue is absence. Women contributed to peace movements, anti-slavery campaigns, labour reform, humanitarian activism, anti-colonial struggles, and human rights advocacy, yet they were often left outside canonical histories. The absence was not accidental. The public world of diplomacy, war, treaty-making, and adjudication was historically treated as male, while care, reproduction, domestic labour, and sexual violence were pushed into the private sphere.

Nationality law gives a clear example. For long periods, many legal systems tied a woman’s nationality to her husband’s status. Marriage could change nationality, create statelessness, or limit independent legal identity. This shows how international law and domestic law combined to treat women’s legal personality as dependent, rather than autonomous (Knop, 2001).

Sexual violence is another central issue. Classical laws of war often addressed honour, family order, and military discipline, but did not treat sexual violence with the seriousness now reflected in modern international criminal law. The ICTY, ICTR, and ICC helped develop legal recognition of rape, sexual slavery, forced pregnancy, and other forms of gendered violence as war crimes, crimes against humanity, and, in certain circumstances, genocide.

Feminist histories also examine labour and care. Global economic law often ignores the unpaid or underpaid work that sustains households, migration systems, health systems, and supply chains. A legal order that protects investment, trade, and property, while treating care work as legally marginal, reflects gendered choices about what counts as economic value.

The public/private divide is central. International law traditionally focused on public acts by states, especially war, treaties, territory, and diplomacy. Feminist approaches show that violence and domination often occur in spaces labelled private: households, workplaces, detention sites, refugee camps, migration routes, and informal economies. A serious legal history must include those spaces, because power does not operate only through formal state acts.

17.3 Marxist and material histories

Marxist and materialist histories ask how international law relates to capitalism, property, labour, extraction, debt, imperialism, and class. Their focus is not only on what legal doctrines say, but also on what economic functions they perform. They examine how law protects property, organises markets, disciplines labour, secures investment, enables extraction, and stabilises unequal economic relations (Miéville, 2005; Marks, 2008).

This approach is useful because many central doctrines of international law have economic effects. Sovereignty defines authority over territory and resources. Treaty law protects commercial commitments. Investment law protects foreign capital. The law of the sea allocates access to fisheries, seabed minerals, shipping routes, and energy resources. Debt law shapes fiscal policy. Trade law structures market access and production.

Material histories also connect the empire with capitalism. Colonialism was not only a political project. It was also a system of extraction, forced labour, land seizure, plantation production, mining, commodity flows, debt, and unequal exchange. Legal doctrines helped organise these relations by defining property, labour status, territorial title, concession rights, company authority, and jurisdiction.

Debt is especially important. A state may be formally sovereign, yet constrained by creditors, financial institutions, bond markets, and conditionality. Materialist analysis shows how legal equality can coexist with economic dependency. It also explains why post-colonial states often demanded permanent sovereignty over natural resources and a New International Economic Order.

Marxist approaches also criticise the image of international law as a neutral referee above politics. They argue that legal form can make unequal relations appear voluntary, especially when contracts, treaties, concessions, and loans are concluded under structural pressure. Formal consent may hide material compulsion.

This does not mean material histories reduce all law to economics. The better point is that legal doctrine must be read with political economy. War, trade, development, investment, debt, labour, and environmental harm cannot be separated neatly. International law helps organise all of them.

17.4 Global intellectual histories

Global intellectual histories widen the field by recovering scholars, diplomats, judges, activists, and legal traditions beyond Europe and North America. This is essential because the discipline’s canon has often treated European writers as universal theorists, while non-European jurists appeared mainly as regional figures, political actors, or later participants.

Latin American contributions are a clear example. Andrés Bello, Carlos Calvo, Luis María Drago, and later Latin American jurists developed important arguments on sovereignty, non-intervention, diplomatic protection, debt, territorial boundaries, and equality. These were not derivative footnotes to European doctrine. They responded to concrete experiences of intervention, financial pressure, recognition struggles, and post-independence state formation (Obregón, 2006).

Asian and African contributions also changed the field. Anti-colonial leaders, diplomats, and jurists used international law to challenge empire, racial discrimination, apartheid, unequal treaties, and economic dependency. Afro-Asian solidarity, Bandung, the Non-Aligned Movement, and UN debates on decolonisation show that legal thought was produced through diplomatic struggle as well as academic writing.

Islamic legal traditions also require serious attention. Rules on truces, envoys, protected persons, captives, commerce, and warfare show that legal regulation of inter-polity relations was not exclusively European. These traditions should not be romanticised or treated as identical to modern international law, but they belong to the broader intellectual history of legal order across communities.

Global intellectual history also changes how we read the canon. Grotius, Vattel, Westphalia, and the European law of nations remain important, but they cannot stand as the whole of history. Their ideas must be placed beside Indigenous legal claims, African anti-colonial arguments, Asian critiques of unequal treaties, Latin American doctrines of non-intervention, Islamic legal thought, and Third World demands for economic justice.

The benefit is analytical accuracy. International law did not become global simply because European ideas spread. It became global through conquest, resistance, adaptation, translation, institutional struggle, and legal creativity by many people. A credible history must show that international legal thought was produced in many locations, under very different conditions of power.

17.5 History as legal argument

History is often used strategically in international law. States invoke historical title in territorial disputes. Courts interpret treaties through their drafting context. Governments cite past practice to support custom. Institutions use founding narratives to defend legitimacy. Scholars construct histories that make certain doctrines appear natural, ancient, universal, or necessary.

This makes history powerful, but dangerous. A historical narrative can clarify legal development, but it can also hide violence, exclusion, and contingency. The story of Westphalia can legitimise sovereignty while hiding empire. The story of civilisation can justify intervention while presenting hierarchy as legal progress. The story of human rights can protect individuals while ignoring selective enforcement. The story of development can promise welfare while concealing economic discipline.

Legal actors often choose histories that support their present claims. A state claiming territory may emphasise old maps, administrative acts, colonial boundaries, or historic usage. A state resisting external scrutiny may invoke sovereignty and non-intervention. A state supporting intervention may invoke human rights, collective security, or historical responsibility. Each argument uses the past to shape the legal meaning of the present.

Courts also use history, but in a disciplined legal way. They may examine travaux préparatoires, prior treaties, state practice, historical administration, colonial instruments, maps, and earlier decisions. Yet courts do not simply discover the past. They select legally relevant facts, assign weight, and connect history to doctrine.

The reader’s task is to ask sharper questions. Which actors are visible in this history? Which are missing? Does the narrative treat law as restraint, justification, or both? Does it make the Empire look accidental? Does it treat Europe as universal? Does it ignore economic power? Does it turn victims into passive objects? Does it make present doctrine look inevitable?

History is not an ornament to international law. It is part of the legal argument itself. For that reason, the final lesson of this article is methodological: to understand international law, readers must study not only rules, but also the histories that make those rules appear legitimate.

Conclusion

The history of International Law is best understood through turning points that changed legal authority, legal subjects, legal sources, institutions, and the relationship between law and power. A simple timeline cannot explain the discipline. The more important question is what each period made legally possible, and what each period made legally invisible.

Ancient treaties showed that political communities needed formal commitments before modern states existed. Roman ius gentium gave later jurists a vocabulary for legal principles operating beyond one local community. Medieval just-war doctrine judged war through authority, cause, intention, and restraint. Iberian expansion exposed the double role of law as a limit on conquest and a language of empire. Grotius systematised arguments about war, commerce, and the sea, while working inside a world of corporate power and maritime rivalry.

Westphalia became a symbol of sovereign statehood, although its mythology often exceeds its legal reality. Enlightenment writers, especially Vattel, made the state the central legal subject. Nineteenth-century positivism professionalised international law, yet tied full legal participation to civilisation, recognition, and imperial hierarchy. The Hague movement, the League, the PCIJ, and the Kellogg-Briand Pact pushed the discipline toward procedure, adjudication, and restrictions on war.

The UN Charter settlement changed the legal order by placing sovereign equality, collective security, human rights, self-determination, peaceful settlement, and the prohibition of force at its centre. Decolonisation transformed membership, challenged the empire, and made self-determination a legal entitlement. Codification, state responsibility, jus cogens, and erga omnes obligations made international law more technical, but also more concerned with community interests. Human rights and international criminal law moved the individual into the legal structure as both rights-holder and potential bearer of responsibility.

Economic globalisation, environmental law, climate change, law of the sea, cyber operations, and space law show that international law now governs fields far beyond classical diplomacy. It regulates markets, resources, ecosystems, data, investment, corporate conduct, and shared risks. These areas also reveal the limits of old doctrines. Sovereignty, consent, responsibility, and jurisdiction remain central, but they are constantly tested by material inequality, private power, ecological harm, and technological change.

The strongest conclusion is not a naive progress story. International law has restrained power, but it has also served power. It has protected states against aggression, people against colonial domination, individuals against atrocity, and communities against some forms of exploitation. It has also justified conquest, organised empire, protected unequal economic structures, and given legal form to hierarchy.

That double character is exactly why the history of International Law matters. It teaches readers to treat legal doctrine with seriousness, but not innocence. Sovereignty can protect self-government, yet shield abuse. Human rights can defend dignity, yet be applied selectively. Self-determination can liberate peoples, yet leave Indigenous dispossession unresolved. State responsibility can clarify breach, yet depend on weak enforcement. Economic law can support cooperation, yet narrow democratic policy space.

A serious study of the history of International Law helps readers understand why current doctrines such as sovereignty, self-determination, human rights, use of force, state responsibility, and global governance remain legally important and politically contested. The discipline’s past does not provide simple answers. It gives something more useful: a clearer view of how law restrains power, how law serves power, and how legal arguments can be used to challenge both.

References

1. Aboul-Enein, Y.H. and Zuhur, S. (2004) Islamic Rulings on Warfare. Carlisle, PA: Strategic Studies Institute, U.S. Army War College. Available at: https://press.armywarcollege.edu/monographs/762/ (Accessed: 14 June 2026).

2. Agreement on Trade-Related Aspects of Intellectual Property Rights (1994) [online]. Available at: https://www.wto.org/english/docs_e/legal_e/27-trips_01_e.htm (Accessed: 14 June 2026).

3. Anghie, A. (2005) Imperialism, Sovereignty and the Making of International Law. Cambridge: Cambridge University Press.

4. Aquinas, T. (1947) Summa Theologica. Translated by Fathers of the English Dominican Province. New York: Benziger Brothers.

5. Augustine of Hippo (1998) The City of God against the Pagans. Edited and translated by R.W. Dyson. Cambridge: Cambridge University Press.

6. Buckland, W.W. (1963) A Text-Book of Roman Law from Augustus to Justinian. 3rd edn. Revised by P. Stein. Cambridge: Cambridge University Press.

7. Carnahan, B.M. (1998) ‘Lincoln, Lieber and the laws of war: the origins and limits of the principle of military necessity’, American Journal of International Law, 92(2), pp. 213–231.

8. Cassel, P.K. (2012) Grounds of Judgment: Extraterritoriality and Imperial Power in Nineteenth-Century China and Japan. Oxford: Oxford University Press.

9. Charlesworth, H. and Chinkin, C. (2000) The Boundaries of International Law: A Feminist Analysis. Manchester: Manchester University Press.

10. Chimni, B.S. (2006) ‘Third World approaches to international law: a manifesto’, International Community Law Review, 8(1), pp. 3–27.

11. Convention on the Prevention and Punishment of the Crime of Genocide (1948) [online]. Available at: https://www.ohchr.org/en/instruments-mechanisms/instruments/convention-prevention-and-punishment-crime-genocide (Accessed: 14 June 2026).

12. Covenant of the League of Nations (1919) [online]. Available at: https://avalon.law.yale.edu/20th_century/leagcov.asp (Accessed: 14 June 2026).

13. Craven, M. (2015) ‘Between law and history: the Berlin Conference of 1884–1885 and the logic of free trade’, London Review of International Law, 3(1), pp. 31–59.

14. Eslava, L., Fakhri, M. and Nesiah, V. (eds.) (2017) Bandung, Global History, and International Law: Critical Pasts and Pending Futures. Cambridge: Cambridge University Press.

15. Gaius (1988) The Institutes of Gaius. Translated by W.M. Gordon and O.F. Robinson. London: Duckworth.

16. Gardiner, R.K. (2015) Treaty Interpretation. 2nd edn. Oxford: Oxford University Press.

17. General Act of the Berlin Conference on West Africa (1885) [online]. Available at: https://archiv.diplo.de/arc-en/the-political-archive/general-act-2684414 (Accessed: 14 June 2026).

18. General Agreement on Tariffs and Trade (1947) [online]. Available at: https://www.wto.org/english/docs_e/legal_e/gatt47_01_e.htm (Accessed: 14 June 2026).

19. Geneva Conventions (1949) [online]. Available at: https://ihl-databases.icrc.org/en/ihl-treaties (Accessed: 14 June 2026).

20. Gong, G.W. (1984) The Standard of ‘Civilization’ in International Society. Oxford: Clarendon Press.

21. Gray, C. (2018) International Law and the Use of Force. 4th edn. Oxford: Oxford University Press.

22. Grotius, H. (2004) The Free Sea. Edited by D. Armitage. Translated by R. Hakluyt. Indianapolis: Liberty Fund.

23. Hague Convention (II) with Respect to the Laws and Customs of War on Land (1899) [online]. Available at: https://ihl-databases.icrc.org/en/ihl-treaties/hague-conv-ii-1899 (Accessed: 14 June 2026).

24. Hague Convention (IV) Respecting the Laws and Customs of War on Land (1907) [online]. Available at: https://ihl-databases.icrc.org/en/ihl-treaties/hague-conv-iv-1907 (Accessed: 14 June 2026).

25. Hathaway, O.A. and Shapiro, S.J. (2017) The Internationalists: How a Radical Plan to Outlaw War Remade the World. New York: Simon & Schuster.

26. International Bank for Reconstruction and Development (1944) Articles of Agreement of the International Bank for Reconstruction and Development [online]. Available at: https://thedocs.worldbank.org/en/doc/722361541184234501-0330022018/original/IBRDArticlesOfAgreementEnglish.pdf (Accessed: 14 June 2026).

27. International Convention on the Settlement of Investment Disputes between States and Nationals of Other States (1965) [online]. Available at: https://icsid.worldbank.org/sites/default/files/ICSID%20Convention%20English.pdf (Accessed: 14 June 2026).

28. International Court of Justice (1945) Statute of the International Court of Justice [online]. Available at: https://www.icj-cij.org/statute (Accessed: 15 June 2026).

29. International Court of Justice (1970) Barcelona Traction, Light and Power Company, Limited, Judgment of 5 February 1970 [online]. Available at: https://www.icj-cij.org/sites/default/files/case-related/50/050-19700205-JUD-01-00-EN.pdf (Accessed: 15 June 2026).

30. International Court of Justice (2010) Pulp Mills on the River Uruguay, Judgment of 20 April 2010 [online]. Available at: https://www.icj-cij.org/sites/default/files/case-related/135/135-20100420-JUD-01-00-EN.pdf (Accessed: 15 June 2026).

31. International Court of Justice (2019) Legal Consequences of the Separation of the Chagos Archipelago from Mauritius in 1965, Advisory Opinion of 25 February 2019 [online]. Available at: https://www.icj-cij.org/sites/default/files/case-related/169/169-20190225-ADV-01-00-EN.pdf (Accessed: 15 June 2026).

32. International Court of Justice (2025) Obligations of States in respect of Climate Change, Advisory Opinion of 23 July 2025 [online]. Available at: https://www.icj-cij.org/node/205614 (Accessed: 15 June 2026).

33. International Covenant on Civil and Political Rights (1966) [online]. Available at: https://www.ohchr.org/en/instruments-mechanisms/instruments/international-covenant-civil-and-political-rights (Accessed: 15 June 2026).

34. International Covenant on Economic, Social and Cultural Rights (1966) [online]. Available at: https://www.ohchr.org/en/instruments-mechanisms/instruments/international-covenant-economic-social-and-cultural-rights (Accessed: 15 June 2026).

35. International Criminal Tribunal for Rwanda (1998) Prosecutor v Jean-Paul Akayesu, Judgment of 2 September 1998 [online]. Available at: https://unictr.irmct.org/sites/unictr.org/files/case-documents/ictr-96-4/trial-judgements/en/980902.pdf (Accessed: 15 June 2026).

36. International Labour Organization (1989) Indigenous and Tribal Peoples Convention, 1989 (No. 169) [online]. Available at: https://normlex.ilo.org/dyn/nrmlx_en/f?p=NORMLEXPUB:12100:0::NO::P12100_INSTRUMENT_ID:312314 (Accessed: 15 June 2026).

37. International Law Commission (2001) Draft Articles on Responsibility of States for Internationally Wrongful Acts, with Commentaries [online]. Available at: https://legal.un.org/ilc/texts/instruments/english/commentaries/9_6_2001.pdf (Accessed: 15 June 2026).

38. International Law Commission (2018) Draft Conclusions on Identification of Customary International Law, with Commentaries [online]. Available at: https://legal.un.org/ilc/texts/instruments/english/commentaries/1_13_2018.pdf (Accessed: 15 June 2026).

39. International Law Commission (2022) Draft Conclusions on Identification and Legal Consequences of Peremptory Norms of General International Law (jus cogens), with Commentaries [online]. Available at: https://legal.un.org/ilc/texts/instruments/english/commentaries/1_14_2022.pdf (Accessed: 15 June 2026).

40. International Military Tribunal (1946) Judgment of the International Military Tribunal for the Trial of German Major War Criminals [online]. Available at: https://avalon.law.yale.edu/imt/09-30-46.asp (Accessed: 15 June 2026).

41. International Military Tribunal for the Far East (1948) Judgment of the International Military Tribunal for the Far East [online]. Available at: https://www.legal-tools.org/doc/fb16ff/pdf/ (Accessed: 15 June 2026).

42. International Monetary Fund (1944) Articles of Agreement of the International Monetary Fund [online]. Available at: https://www.imf.org/external/pubs/ft/aa/ (Accessed: 15 June 2026).

43. International Tribunal for the Law of the Sea (2024) Request for an Advisory Opinion Submitted by the Commission of Small Island States on Climate Change and International Law, Advisory Opinion of 21 May 2024 [online]. Available at: https://www.itlos.org/fileadmin/itlos/documents/cases/31/Advisory_Opinion/C31_Adv_Op_21.05.2024_orig.pdf (Accessed: 15 June 2026).

44. Kellogg-Briand Pact (1928) General Treaty for Renunciation of War as an Instrument of National Policy [online]. Available at: https://avalon.law.yale.edu/20th_century/kbpact.asp (Accessed: 15 June 2026).

45. Khadduri, M. (1966) The Islamic Law of Nations: Shaybani’s Siyar. Baltimore: Johns Hopkins Press.

46. Klabbers, J. (2023) International Law. 4th edn. Cambridge: Cambridge University Press.

47. Knop, K. (1993) ‘Re/Statements: feminism and state sovereignty in international law’, Transnational Law and Contemporary Problems, 3, pp. 293–344.

48. Koskenniemi, M. (2001) The Gentle Civilizer of Nations: The Rise and Fall of International Law 1870–1960. Cambridge: Cambridge University Press.

49. Koskenniemi, M. (2011) ‘Histories of international law: dealing with Eurocentrism’, Rechtsgeschichte, 19, pp. 152–177.

50. Krasner, S.D. (1999) Sovereignty: Organized Hypocrisy. Princeton: Princeton University Press.

51. Langdon, S. and Gardiner, A.H. (1920) ‘The treaty of alliance between Ḫattušili, King of the Hittites, and the Pharaoh Ramesses II of Egypt’, The Journal of Egyptian Archaeology, 6(3), pp. 179–205.

52. Lesaffer, R. (ed.) (2004) Peace Treaties and International Law in European History: From the Late Middle Ages to World War One. Cambridge: Cambridge University Press.

53. Marks, S. (ed.) (2008) International Law on the Left: Re-examining Marxist Legacies. Cambridge: Cambridge University Press.

54. Marrakesh Agreement Establishing the World Trade Organization (1994) [online]. Available at: https://www.wto.org/english/docs_e/legal_e/04-wto_e.htm (Accessed: 15 June 2026).

55. Meron, T. (2000) ‘The Martens Clause, principles of humanity, and dictates of public conscience’, American Journal of International Law, 94(1), pp. 78–89.

56. Miéville, C. (2005) Between Equal Rights: A Marxist Theory of International Law. Leiden: Brill.

57. Moore, J.B. (1898) History and Digest of the International Arbitrations to Which the United States Has Been a Party. Washington, DC: Government Printing Office.

58. Muldoon, J. (1979) Popes, Lawyers, and Infidels: The Church and the Non-Christian World 1250–1550. Philadelphia: University of Pennsylvania Press.

59. Obregón, L. (2006) ‘Between civilization and barbarism: Creole interventions in international law’, Third World Quarterly, 27(5), pp. 815–832.

60. Osiander, A. (2001) ‘Sovereignty, international relations, and the Westphalian myth’, International Organization, 55(2), pp. 251–287.

61. Pagden, A. (1995) Lords of All the World: Ideologies of Empire in Spain, Britain and France c.1500–c.1800. New Haven: Yale University Press.

62. Paris Agreement (2015) [online]. Available at: https://unfccc.int/sites/default/files/english_paris_agreement.pdf (Accessed: 16 June 2026).

63. Permanent Court of International Justice (1928) Factory at Chorzów, Merits, Judgment No. 13 [online]. Available at: https://www.icj-cij.org/sites/default/files/permanent-court-of-international-justice/serie_A/A_17/54_Usine_de_Chorzow_Fond_Arret.pdf (Accessed: 16 June 2026).

64. Pope Alexander VI (1493) Inter caetera [online]. Available at: https://www.papalencyclicals.net/alex06/alex06inter.htm (Accessed: 16 June 2026).

65. Pope Nicholas V (1452) Dum Diversas [online]. Available at: https://www.papalencyclicals.net/nichol05/dum-diversas.htm (Accessed: 16 June 2026).

66. Pope Nicholas V (1455) Romanus Pontifex [online]. Available at: https://www.papalencyclicals.net/nichol05/romanus-pontifex.htm (Accessed: 16 June 2026).

67. Rome Statute of the International Criminal Court (1998) [online]. Available at: https://www.icc-cpi.int/sites/default/files/RS-Eng.pdf (Accessed: 16 June 2026).

68. Schiller, A.A. (1978) Roman Law: Mechanisms of Development. The Hague: Mouton.

69. Sherwin-White, A.N. (1973) The Roman Citizenship. 2nd edn. Oxford: Oxford University Press.

70. Simpson, G. (2004) Great Powers and Outlaw States: Unequal Sovereigns in the International Legal Order. Cambridge: Cambridge University Press.

71. Treaty of Tordesillas (1494) Treaty between Spain and Portugal Concluded at Tordesillas, 7 June 1494 [online]. Available at: https://avalon.law.yale.edu/15th_century/mod001.asp (Accessed: 16 June 2026).

72. Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies (1967) [online]. Available at: https://www.unoosa.org/oosa/en/ourwork/spacelaw/treaties/outerspacetreaty.html (Accessed: 16 June 2026).

73. United Nations (1945) Charter of the United Nations [online]. Available at: https://www.un.org/en/about-us/un-charter/full-text (Accessed: 16 June 2026).

74. United Nations (1982) United Nations Convention on the Law of the Sea [online]. Available at: https://www.un.org/depts/los/convention_agreements/texts/unclos/unclos_e.pdf (Accessed: 16 June 2026).

75. United Nations Conference on Environment and Development (1992) Rio Declaration on Environment and Development [online]. Available at: https://www.un.org/en/development/desa/population/migration/generalassembly/docs/globalcompact/A_CONF.151_26_Vol.I_Declaration.pdf (Accessed: 16 June 2026).

76. United Nations Conference on the Human Environment (1972) Declaration of the United Nations Conference on the Human Environment [online]. Available at: https://documents.un.org/doc/undoc/gen/nl7/300/05/pdf/nl730005.pdf (Accessed: 16 June 2026).

77. United Nations Framework Convention on Climate Change (1992) [online]. Available at: https://unfccc.int/files/essential_background/background_publications_htmlpdf/application/pdf/conveng.pdf (Accessed: 16 June 2026).

78. United Nations General Assembly (1960) Declaration on the Granting of Independence to Colonial Countries and Peoples, Resolution 1514 (XV) [online]. Available at: https://digitallibrary.un.org/record/206943 (Accessed: 17 June 2026).

79. United Nations General Assembly (1962) Permanent Sovereignty over Natural Resources, Resolution 1803 (XVII) [online]. Available at: https://digitallibrary.un.org/record/203965 (Accessed: 17 June 2026).

80. United Nations General Assembly (1974) Declaration on the Establishment of a New International Economic Order, Resolution 3201 (S-VI) [online]. Available at: https://digitallibrary.un.org/record/218450 (Accessed: 17 June 2026).

81. United Nations General Assembly (2007) United Nations Declaration on the Rights of Indigenous Peoples, Resolution 61/295 [online]. Available at: https://www.ohchr.org/en/indigenous-peoples/un-declaration-rights-indigenous-peoples (Accessed: 17 June 2026).

82. United Nations Human Rights Council (2011) Guiding Principles on Business and Human Rights: Implementing the United Nations “Protect, Respect and Remedy” Framework [online]. Available at: https://www.ohchr.org/documents/publications/guidingprinciplesbusinesshr_en.pdf (Accessed: 17 June 2026).

83. United States War Department (1863) Instructions for the Government of Armies of the United States in the Field: General Orders No. 100 (Lieber Code) [online]. Available at: https://ihl-databases.icrc.org/en/ihl-treaties/liebercode-1863 (Accessed: 17 June 2026).

84. Vadi, V. (2017) ‘International law and its histories: methodological risks and opportunities’, Harvard International Law Journal, 58(2), pp. 311–352.

85. van Ittersum, M.J. (2006) Profit and Principle: Hugo Grotius, Natural Rights Theories and the Rise of Dutch Power in the East Indies, 1595–1615. Leiden: Brill.

86. Vattel, E. de (2008) The Law of Nations. Edited by B. Kapossy and R. Whatmore. Indianapolis: Liberty Fund.

87. Vienna Convention on the Law of Treaties (1969) [online]. Available at: https://legal.un.org/ilc/texts/instruments/english/conventions/1_1_1969.pdf (Accessed: 17 June 2026).

88. Vitoria, F. de (1991) Political Writings. Edited by A. Pagden and J. Lawrance. Cambridge: Cambridge University Press.

89. Watson, A. (1992) The State, Law, and Religion: Pagan Rome. Athens: University of Georgia Press.