Law of the Sea Notes
Introduction
Effective law of the sea notes need to connect legal rules to the maritime setting in which they operate. For revision, examination problems, and initial research, identifying the activity is as important as calculating the distance from shore. A foreign vessel operating within a coastal State’s exclusive economic zone, for example, may enjoy freedom of navigation, require consent for marine scientific research, need authorization to exploit natural resources, or exercise rights associated with laying submarine cables. The legal consequences depend on both location and conduct.
The 1982 United Nations Convention on the Law of the Sea provides the central framework. It establishes distinct regimes for internal waters, the territorial sea, the contiguous zone, the exclusive economic zone, the continental shelf, the high seas, and the international seabed Area. These regimes do not form a single horizontal sequence. The water column and seabed may be governed differently: continental-shelf rights concern the seabed and subsoil, while the waters above may form part of an EEZ or, farther offshore, the high seas (United Nations, 1982).
Several distinctions determine whether an answer is legally accurate. Sovereignty over the territorial sea differs from the sovereign rights and specified jurisdiction exercised in the EEZ; continental-shelf rights do not amount to control of the water column; and a State’s entitlement to maritime areas is separate from the delimitation of overlapping entitlements with another State. On the high seas, navigation and other freedoms predominate, while mineral resources of the Area are governed by the separate common-heritage regime.
A reliable analysis begins by locating the conduct within the relevant maritime regime and identifying the legal competence actually engaged. Rules on navigation, resources, research, environmental protection, enforcement, and boundary disputes can then be applied in the correct legal setting. This method also prevents a common revision error: recalling a UNCLOS rule without identifying where it applies, which State or actor holds the relevant right or duty, and what legal source supports the conclusion.
1. How to Read Law of the Sea Notes
UNCLOS is the central treaty of the modern law of the sea, but it does not exhaust the subject. The 1982 Convention supplies the basic structure for maritime zones, navigation, resources, environmental protection, marine scientific research, and dispute settlement. Customary international law remains independently relevant, particularly where a State is not party to UNCLOS or where a treaty provision is invoked as a rule binding more generally.
Other instruments operate alongside the Convention. The four 1958 Geneva Conventions remain in force for their parties; the 1994 Part XI Agreement modified the implementation of the deep-seabed regime; the 1995 UN Fish Stocks Agreement develops the rules governing straddling and highly migratory stocks; and the 2023 BBNJ Agreement, in force since 17 January 2026, regulates aspects of marine biodiversity beyond national jurisdiction. IMO conventions and standards also shape areas such as navigation safety and marine pollution.
Treaty law and customary international law must be kept separate. In the North Sea Continental Shelf cases, the International Court of Justice rejected the argument that the equidistance rule in Article 6 of the 1958 Continental Shelf Convention bound the Federal Republic of Germany, which was not a party to that Convention. The Court separately examined whether the rule had customary status and concluded that it did not bind Germany on that basis (ICJ, 1969). UNCLOS provisions should be approached with the same discipline: customary status must be assessed rule by rule.
Four distinctions organize much of the subject. Sovereignty describes the territorial authority exercised in areas such as internal waters and the territorial sea; sovereign rights are narrower, functional rights connected to specified activities and resources. Prescriptive jurisdiction—the authority to make rules—must also be distinguished from enforcement jurisdiction, because the existence of a regulatory power does not automatically authorize boarding, arrest, or detention.
Entitlement and delimitation answer different questions. Entitlement concerns the maritime zones a coast or qualifying feature is capable of generating. Delimitation concerns the division of overlapping entitlements between States. A further distinction separates the water column from the seabed and subsoil, since the legal regime governing resources beneath the sea may differ from the regime governing navigation and other activities above them.
These distinctions provide the working vocabulary for the wider law of the sea framework and prevent many of the errors that arise when UNCLOS provisions are memorized without their geographic and legal context.
2. Maritime Zones Under UNCLOS
Maritime zones are measured from baselines and allocate different forms of coastal-State authority. The normal baseline is the low-water line along the coast, while UNCLOS permits special methods in defined geographic circumstances. Once the baseline is established, it becomes the reference point for measuring the territorial sea, contiguous zone, EEZ, and other maritime limits.
Maritime regime | Geographic basis | Coastal-State position | Rights of other States | Main UNCLOS provisions |
Internal waters | Landward of the baseline | Sovereignty | Generally no passage right, subject to Article 8(2) | Arts. 2, 8 |
Territorial sea | Up to 12 nm from baselines | Sovereignty over waters, seabed, subsoil, and airspace | Innocent passage for ships | Arts. 2–3, 17–32 |
Contiguous zone | Outer limit of 24 nm from baselines | Limited control for customs, fiscal, immigration, and sanitary purposes | Rights under the underlying EEZ or high-seas regime | Art. 33 |
Exclusive economic zone | Beyond territorial sea, up to 200 nm | Sovereign rights over resources and specified jurisdiction | Navigation, overflight, cables, pipelines, related lawful uses | Arts. 55–58 |
Continental shelf | Seabed and subsoil to at least 200 nm where applicable; possibly farther under Art. 76 | Inherent and exclusive sovereign rights over shelf resources | Rights concerning superjacent waters, cables, and pipelines subject to UNCLOS | Arts. 76–81 |
High seas | Waters falling within Article 86 | No coastal-State sovereignty | High-seas freedoms subject to UNCLOS | Arts. 86–115 |
The Area | Seabed, ocean floor, and subsoil beyond national jurisdiction | No national sovereignty; resources governed under the common-heritage regime | Activities governed through Part XI and the ISA system | Arts. 1(1)(1), 136–153 |
Straight baselines are exceptional. Article 7 permits them where a coastline is deeply indented and cut into or where a fringe of islands lies along the coast in its immediate vicinity. In the Fisheries Case, the ICJ upheld Norway’s system along its highly irregular, island-fringed coast while confirming that the legality of maritime claims is governed by international law (ICJ, 1951). UNCLOS later codified and refined the conditions for using straight baselines.
Maritime features require classification before their legal effect can be assessed. An island under Article 121(1) is a naturally formed area of land, surrounded by water and above water at high tide, and normally generates the same maritime zones as other land territory. Article 121(3), however, denies an EEZ and continental shelf to rocks that cannot sustain human habitation or economic life of their own. Low-tide elevations do not normally generate maritime zones independently, while artificial islands have no territorial sea or other maritime entitlement of their own.
The South China Sea Arbitration gave Article 121(3) its most detailed judicial interpretation. The tribunal assessed features in their natural condition rather than by reference to artificial reclamation or externally supported installations, and concluded that none of the Spratly Islands’ high-tide features generated an EEZ or continental shelf (PCA, 2016). The award binds the parties, China rejects it, and aspects of its reasoning remain debated, but it remains a central authority for understanding the legal consequences of maritime-feature classification.
The main zones then distribute authority differently. Internal waters and the territorial sea fall under coastal-State sovereignty, although the territorial sea is subject to innocent passage. The contiguous zone gives the coastal State only limited control connected to customs, fiscal, immigration, and sanitary laws; it is not an additional belt of sovereign territory.
The allocation of rights and jurisdiction in the exclusive economic zone is narrower than territorial sovereignty. The coastal State has sovereign rights over natural resources and specified jurisdiction over matters including installations, marine scientific research, and protection of the marine environment. Other States retain navigation, overflight, cable, pipeline, and related lawful-use freedoms under Article 58.
Continental-shelf rights are different again. They concern the seabed and subsoil, exist inherently, and do not depend on occupation or an express proclamation. A State may therefore possess continental-shelf rights even where it has not proclaimed an EEZ.
Beyond national jurisdiction, the water column and seabed must still be separated. High-seas freedoms govern the waters where Article 86 applies. The seabed beneath may instead form part of a coastal State’s outer continental shelf or, beyond national jurisdiction, the Area, whose mineral resources are governed by the common heritage of mankind principle under Part XI.
3. Navigation and Enforcement at Sea
In the territorial sea, Article 17 gives ships of all States a right of innocent passage. The first question is whether the vessel is actually engaged in “passage” under Article 18. Navigation must be continuous and expeditious, although stopping and anchoring remain compatible with passage when incidental to ordinary navigation, required by force majeure or distress, or undertaken to assist persons, ships, or aircraft in danger.
The second question is whether that passage remains innocent. Article 19 treats passage as non-innocent when a vessel engages in specified conduct prejudicial to the peace, good order, or security of the coastal State. The list includes weapons exercises, intelligence collection prejudicial to coastal defense or security, fishing, research or survey activities, serious willful pollution, and other activity not having a direct bearing on passage.
Coastal-State regulation is limited by UNCLOS. Article 21 permits laws on specified subjects, while Article 25 allows necessary measures against passage that is not innocent and narrowly permits temporary suspension of innocent passage in specified areas when essential for security and duly published. Submarines exercising innocent passage must navigate on the surface and show their flag under Article 20.
Warships remain a point of disagreement. UNCLOS refers to passage by “ships of all States” and contains provisions specifically governing warships, while a number of coastal States require prior authorization or notification. Maritime powers reject those requirements. The treaty does not expressly settle that broader controversy, so it should be treated as a genuine division in State practice rather than reduced to a categorical rule.
Transit passage is broader. In qualifying straits used for international navigation, ships and aircraft may exercise navigation and overflight for continuous and expeditious transit in their normal mode. Submarines may remain submerged, aircraft have an overflight right, and transit passage cannot be suspended. Archipelagic sea-lanes passage performs a comparable function through qualifying routes across archipelagic waters.
Corfu Channel supplies an important judicial foundation without itself creating the later UNCLOS transit-passage regime. The ICJ held that warships in peacetime could pass through a strait used for international navigation between two parts of the high seas without prior authorization, provided the passage was innocent (ICJ, 1949). UNCLOS subsequently developed a more extensive treaty regime for international straits.
On the high seas, Article 92 establishes exclusive flag-State jurisdiction as the starting rule. Article 110 creates a limited right of visit where there are reasonable grounds for suspecting piracy, slave trading, unauthorized broadcasting in circumstances falling within Article 109, statelessness, or a vessel falsely claiming foreign nationality while actually sharing the warship’s nationality.
Hot pursuit under Article 111 is a different doctrine. It permits coastal enforcement lawfully begun in specified maritime zones to continue onto the high seas when the cumulative treaty conditions are met. In M/V Saiga (No. 2), ITLOS applied those conditions strictly and stated that force in maritime enforcement should be avoided where possible and, when unavoidable, must not exceed what is reasonable and necessary (ITLOS, 1999).
Piracy is the classic exception to exclusive flag-State enforcement. UNCLOS permits every State, subject to Articles 100–107, to seize a pirate ship on the high seas or in another place outside the jurisdiction of any State and to prosecute those responsible. This makes piracy unusual: most forms of high-seas enforcement still require a separate treaty basis, flag-State consent, or another recognized jurisdictional ground.
4. Resources, Fisheries, and the Marine Environment
The EEZ gives the coastal State significant resource powers without converting the zone into sovereign territory. Article 56 grants sovereign rights for exploring, exploiting, conserving, and managing living and non-living natural resources, together with specified jurisdiction over installations, marine scientific research, and protection of the marine environment. Other States continue to exercise the freedoms protected by Article 58.
Fisheries law combines conservation, utilization, and enforcement. Article 61 requires the coastal State to determine the allowable catch and adopt conservation measures designed to prevent over-exploitation, taking account of the best scientific evidence available. Article 62 then requires the coastal State to promote optimum utilization of the living resources.
Where the coastal State lacks capacity to harvest the entire allowable catch, Article 62(2) requires it, through agreements or other arrangements, to give other States access to the surplus, having regard to the factors specified by UNCLOS. That obligation does not create a general freedom for foreign vessels to enter an EEZ and fish. Access remains subject to the treaty framework, applicable arrangements, and lawful coastal-State conditions.
Article 73 provides the principal enforcement tools for EEZ fisheries. The coastal State may board, inspect, arrest, and institute judicial proceedings to secure compliance with its laws. Arrested vessels and crews must be promptly released upon the posting of a reasonable bond or other security, and penalties may not include imprisonment, in the absence of contrary agreements between the States concerned, or corporal punishment. The flag State must also receive prompt notification of arrests and penalties.
The continental shelf adds another legal title to resource questions. Article 77 gives the coastal State exclusive rights over mineral and other non-living resources of the seabed and subsoil, together with sedentary species. Articles 79 and 80 regulate cables, pipelines, and installations on the shelf. The coastal State’s consent is required for delineating the course of pipelines, but UNCLOS does not give an equivalent general approval power over the route of transiting submarine cables.
Marine scientific research is subject to its own regime. Research in a coastal State’s EEZ or continental shelf is generally conducted with that State’s consent under Article 246. In normal circumstances, however, the coastal State is required to grant consent for research undertaken exclusively for peaceful purposes and intended to increase scientific knowledge of the marine environment for the benefit of humanity. Article 246(5) identifies circumstances in which the coastal State may withhold consent.
Environmental duties cut across these separate zones. Article 192 establishes the general obligation to protect and preserve the marine environment. Article 194 requires States to take necessary measures, using the best practicable means at their disposal and in accordance with their capabilities, to prevent, reduce, and control marine pollution. UNCLOS also contains duties concerning cooperation, monitoring, and environmental assessment where the relevant treaty thresholds are met.
The 2024 ITLOS climate advisory opinion applied these obligations directly to anthropogenic greenhouse-gas emissions. The Tribunal concluded that such emissions constitute pollution of the marine environment for UNCLOS purposes and treated Article 194(1) as imposing a due-diligence obligation of conduct (ITLOS, 2024). The International Court of Justice subsequently considered law-of-the-sea obligations within its broader 2025 advisory opinion on States’ climate obligations, giving substantial weight to the earlier ITLOS interpretation (ICJ, 2025).
The BBNJ Agreement now adds a further treaty layer beyond national jurisdiction. Adopted in 2023 and in force since 17 January 2026, it addresses marine genetic resources, area-based management tools, environmental impact assessment, and capacity-building in areas beyond national jurisdiction. Its rules operate alongside the established UNCLOS regimes rather than replacing the high-seas framework or the separate Part XI system governing mineral resources of the Area.
5. Maritime Delimitation and the Cases to Remember
Maritime delimitation begins only after entitlement has been established. Entitlement asks what maritime zones a coast or qualifying feature can generate; delimitation asks how overlapping entitlements belonging to different States are divided. For revision, the sequence is straightforward: baseline and relevant coast → feature classification → maritime entitlement → overlap → delimitation.
Article 15 governs territorial-sea delimitation between States with opposite or adjacent coasts. In the absence of agreement, neither State is normally entitled to extend its territorial sea beyond the median line, unless historic title or other special circumstances justify a different boundary. Articles 74 and 83 use different language for the EEZ and continental shelf: delimitation must be achieved by agreement on the basis of international law in order to reach an equitable solution.
UNCLOS does not itself prescribe the three-stage methodology now commonly associated with EEZ and continental-shelf delimitation. That method developed through judicial interpretation. In Maritime Delimitation in the Black Sea, the ICJ constructed a provisional equidistance line, considered whether relevant circumstances justified adjustment, and then checked whether the resulting boundary produced a marked disproportionality between the relevant coastal lengths and maritime areas allocated to the parties (ICJ, 2009). The final stage is an equity check, not a requirement to divide maritime space according to a fixed mathematical ratio.
Cases are easier to remember when each is tied to a particular legal proposition. Fisheries belongs with straight baselines; North Sea Continental Shelf with customary international law and the development of shelf delimitation; the South China Sea Arbitration with maritime-feature classification and entitlement; Black Sea with the modern delimitation method; and Nicaragua v Colombia with continental-shelf entitlement beyond 200 nautical miles.
The 2023 Nicaragua v Colombia judgment is especially useful for distinguishing entitlement from delimitation. The ICJ held, under customary international law, that a State’s continental-shelf entitlement beyond 200 nautical miles may not extend within 200 nautical miles of another State’s baselines. Because Nicaragua had no overlapping entitlement in the relevant area, there was nothing for the Court to delimit (ICJ, 2023).
6. UNCLOS Dispute Settlement
A substantive UNCLOS claim does not automatically give an international court or tribunal jurisdiction. Part XV begins with peaceful settlement. Articles 279 and 280 preserve the parties’ freedom to choose peaceful means, while Article 283 requires an expeditious exchange of views concerning settlement when a dispute arises.
Where compulsory procedures are available, Article 287 identifies four principal forums: the International Tribunal for the Law of the Sea, the International Court of Justice, Annex VII arbitration, and Annex VIII special arbitration for specified categories of disputes. A State may select one or more procedures by declaration. If no applicable choice has been made, Annex VII arbitration operates as the default; it also ordinarily applies where the parties have accepted different procedures and have not agreed on another forum.
Compulsory settlement has limits. Article 297 restricts jurisdiction over particular categories, including aspects of marine scientific research and EEZ fisheries. Article 298 allows States, by declaration, to exclude certain maritime-delimitation and historic-title disputes, military activities, and law-enforcement activities connected to the exercise of sovereign rights or jurisdiction excluded under Article 297(2) or (3). Compulsory conciliation remains available in some situations even where binding adjudication is excluded.
How a dispute is characterized can determine jurisdiction. A tribunal empowered to interpret or apply UNCLOS does not acquire general jurisdiction over territorial sovereignty because a claim is framed in Convention language. In the South China Sea Arbitration, the Annex VII tribunal separated land-sovereignty questions, which it did not decide, from questions concerning maritime entitlements and conduct under UNCLOS (South China Sea Arbitration, 2015; 2016).
Two Part XV procedures deserve separate treatment. Article 290 permits provisional measures to preserve the parties’ respective rights or prevent serious harm to the marine environment while a dispute is pending. Article 292 addresses qualifying cases in which a detained vessel or crew has allegedly not been promptly released despite the posting of a reasonable bond or other financial security. Neither procedure determines the final merits of the underlying dispute.
7. How to Answer a Law of the Sea Problem
A reliable law of the sea answer follows a fixed legal sequence: identify the maritime zone → identify the relevant actor → identify the legal source → state the right or obligation → test exceptions and competing rights → identify enforcement authority → determine the available forum or remedy. This prevents a common mistake: finding the correct UNCLOS provision but applying it in the wrong maritime space or to the wrong legal relationship.
Consider a foreign vessel operating 150 nautical miles from the baselines within a coastal State’s EEZ. Navigation is protected by Article 58. Fishing engages the coastal State’s sovereign rights and fisheries regime. Marine scientific research ordinarily falls within the Article 246 consent framework. Laying a submarine cable engages freedoms protected by Articles 58 and 79. Certain foreign military or intelligence activities remain legally contested. The location has not changed; the legal characterization of the activity has.
Enforcement requires a separate inquiry. Coastal-State regulatory competence does not automatically create an unrestricted right to board or arrest. Fisheries enforcement follows Article 73, pollution enforcement is governed by Part XII, hot pursuit depends on Article 111, and high-seas enforcement normally begins from flag-State exclusivity subject to recognized exceptions.
Revision is most effective when organized around contrasts rather than isolated article numbers. Territorial sea and EEZ separate sovereignty from sovereign rights. EEZ and continental shelf distinguish the water column from the seabed and subsoil. Innocent passage differs from transit passage in scope, overflight, normal-mode operation, and suspension. Islands, rocks, and low-tide elevations produce different maritime consequences, while entitlement must be established before delimitation begins.
The same discipline applies to legal sources. A treaty rule may also reflect customary international law, but the two bases should not be collapsed. A judicial method such as the three-stage delimitation approach is not treaty text, and an arbitral award does not become universally binding merely because its reasoning is influential.
Readers who need fuller case authorities, comparison tables, problem questions, and structured answer frameworks can use the International Law of the Sea Study Guide for more systematic revision after working through these core rules.
Recommended Study Guide
The International Law of the Sea Study Guide is most useful for law and international-relations students, examination candidates, researchers, civil-service or diplomatic-service candidates, and readers who need to study the subject as a connected system rather than resolve one isolated question.
The 98-page 2026 guide develops the main areas covered here in greater depth, including baselines and maritime features, passage regimes, the EEZ, continental shelf, high seas, enforcement, the Area, fisheries, marine environmental protection, scientific research, maritime delimitation, and dispute settlement. It also includes comparison tables, case treatment, revision points, self-assessment questions, answer frameworks, a glossary, and consolidated tables of principal cases and treaties.
A reader looking only for one rule—such as the breadth of the territorial sea, the meaning of innocent passage, or the holding of a single case—may not need the full guide. Its stronger use is systematic course revision, examination preparation, or research requiring the subject’s doctrines and authorities to be organized in one structured reference.
Also read
Conclusion
The law of the sea is easier to apply when UNCLOS is treated as a system allocating different legal competences across different maritime spaces. Distance from the coast matters, but the legal result also depends on the activity involved, the actor asserting authority, and the source of the claimed right or obligation.
Accurate analysis rests on a small number of recurring distinctions: sovereignty versus sovereign rights, water column versus seabed and subsoil, prescription versus enforcement, and entitlement versus delimitation. Once those distinctions are clear, individual UNCLOS provisions and cases become easier to place and apply to new factual problems.
References
Agreement for the Implementation of the Provisions of the United Nations Convention on the Law of the Sea of 10 December 1982 relating to the Conservation and Management of Straddling Fish Stocks and Highly Migratory Fish Stocks (1995) adopted 4 August 1995, entered into force 11 December 2001, 2167 UNTS 3.
Agreement relating to the Implementation of Part XI of the United Nations Convention on the Law of the Sea of 10 December 1982 (1994) adopted 28 July 1994, entered into force 28 July 1996, 1836 UNTS 3.
Agreement under the United Nations Convention on the Law of the Sea on the Conservation and Sustainable Use of Marine Biological Diversity of Areas beyond National Jurisdiction (2023) adopted 19 June 2023, entered into force 17 January 2026, UN registration no. 59087.
Arbitral Tribunal constituted under Annex VII to the United Nations Convention on the Law of the Sea (2015) The South China Sea Arbitration (The Republic of the Philippines v. The People’s Republic of China), Award on Jurisdiction and Admissibility, 29 October 2015, PCA Case No. 2013-19.
Arbitral Tribunal constituted under Annex VII to the United Nations Convention on the Law of the Sea (2016) The South China Sea Arbitration (The Republic of the Philippines v. The People’s Republic of China), Award, 12 July 2016, PCA Case No. 2013-19.
Convention on Fishing and Conservation of the Living Resources of the High Seas (1958) adopted 29 April 1958, entered into force 20 March 1966, 559 UNTS 285.
Convention on the Continental Shelf (1958) adopted 29 April 1958, entered into force 10 June 1964, 499 UNTS 311.
Convention on the High Seas (1958) adopted 29 April 1958, entered into force 30 September 1962, 450 UNTS 11.
Convention on the Territorial Sea and the Contiguous Zone (1958) adopted 29 April 1958, entered into force 10 September 1964, 516 UNTS 205.
International Court of Justice (1949) Corfu Channel (United Kingdom v. Albania), Merits, Judgment, 9 April 1949, ICJ Reports 1949, p. 4.
International Court of Justice (1951) Fisheries (United Kingdom v. Norway), Judgment, 18 December 1951, ICJ Reports 1951, p. 116.
International Court of Justice (1969) North Sea Continental Shelf, Judgment, 20 February 1969, ICJ Reports 1969, p. 3.
International Court of Justice (2009) Maritime Delimitation in the Black Sea (Romania v. Ukraine), Judgment, 3 February 2009, ICJ Reports 2009, p. 61.
International Court of Justice (2023) Question of the Delimitation of the Continental Shelf between Nicaragua and Colombia beyond 200 Nautical Miles from the Nicaraguan Coast (Nicaragua v. Colombia), Judgment, 13 July 2023, ICJ Reports 2023, p. 413.
International Court of Justice (2025) Obligations of States in respect of Climate Change, Advisory Opinion, 23 July 2025.
International Tribunal for the Law of the Sea (1999) M/V “SAIGA” (No. 2) (Saint Vincent and the Grenadines v. Guinea), Judgment, ITLOS Reports 1999, p. 10.
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, 21 May 2024, ITLOS Reports 2024, p. 4.
United Nations Convention on the Law of the Sea (1982) adopted 10 December 1982, entered into force 16 November 1994, 1833 UNTS 3.
