Legal Boundaries of U.S. Military Strikes on Iran

Legal Boundaries of U.S. Military Strikes on Iran became a central focus of international legal discourse following the unprecedented U.S. aerial operation conducted on June 21–22, 2025. The strikes targeted nuclear infrastructure across Iran, including heavily fortified facilities in Fordow, Isfahan, and Natanz. These actions, executed without explicit congressional approval or United Nations authorization, reignited longstanding questions about the legality of unilateral military force under both U.S. constitutional law and international legal norms.

This article critically examines the legal justifications offered by the United States and evaluates their compatibility with established domestic and international legal frameworks. The strike was launched following a series of escalations in the Gulf region, with U.S. officials citing credible intelligence indicating that Iran was accelerating uranium enrichment for weaponization and had coordinated missile strikes on U.S. assets through proxy forces.

The legality of the June 2025 operation must be analyzed in two dimensions: the internal constitutional authority of the President to order military action absent congressional authorization, and the external framework of the United Nations Charter, which governs the use of force among states. At the heart of the issue lies a fundamental tension between executive flexibility in national defense and the legal limits imposed by democratic oversight and international obligations.

While some legal scholars defend the operation under the doctrine of anticipatory self-defense, others argue it constitutes a violation of Article 2(4) of the UN Charter and exceeds the President’s Article II powers under the U.S. Constitution. The absence of transparent congressional consultation and multilateral coordination has further complicated the legitimacy of the strikes in the eyes of both legal experts and international observers.

In assessing the legal boundaries of U.S. military strikes on Iran, this article outlines the constitutional basis for presidential use of force, reviews the applicability of international legal doctrines, and examines global reactions and potential legal consequences. The following sections aim to provide a structured and evidence-based analysis of how legality is interpreted and contested in high-stakes geopolitical conflicts.

Domestic Constitutional & Statutory Authority

The June 2025 U.S. airstrikes on Iranian nuclear facilities triggered intense legal scrutiny over their constitutionality and compliance with existing statutory frameworks. Central to the debate is the question of presidential authority to initiate military action without explicit congressional approval. This section dissects the constitutional provisions, relevant statutes like the War Powers Resolution, and past legal precedents to determine whether the operation fell within the lawful exercise of executive power.

A. The U.S. Constitution and the War Powers Clause

The U.S. Constitution delineates war-making powers between Congress and the Executive. Article I, Section 8 gives Congress the sole authority to declare war, raise and support armies, and regulate military forces. Conversely, Article II designates the President as Commander-in-Chief of the Armed Forces. This division has historically created friction over how far presidential authority extends in the absence of a congressional declaration of war.

In the case of the June 2025 strikes, the President did not seek or obtain congressional authorization prior to launching the operation. The administration justified the action as a necessary defensive measure under Article II powers. However, critics argue this represents an overextension of executive authority. Unlike ongoing hostilities with non-state actors, Iran is a sovereign state, and the scope of presidential authority over state-directed military operations remains legally and politically contested.

B. The War Powers Resolution of 1973

To address growing concerns about unchecked presidential military action, Congress enacted the War Powers Resolution (WPR) in 1973. This statute requires:

• Presidential notification to Congress within 48 hours of introducing U.S. armed forces into hostilities or situations likely to involve hostilities;

• Termination of military operations within 60 days, with a 30-day withdrawal period, unless Congress authorizes continued action;

• Regular reporting to Congress on the scope and progress of hostilities.

The Biden administration did submit a notification to Congress within the required timeframe, but the legal justification offered raised red flags. The President asserted that the strikes were a response to “imminent threats to U.S. personnel and strategic assets,” a phrase reminiscent of the rationale used in past unilateral actions. Critics argue that the WPR was designed precisely to limit such open-ended executive claims.

In this instance, members of Congress from both parties expressed dissatisfaction, citing a lack of meaningful consultation and warning that the operation risked escalating into a broader conflict. Legal scholars noted that compliance with WPR procedural requirements does not automatically legitimize the substance of the military action under constitutional norms.

C. The 2001 and 2002 Authorizations for Use of Military Force (AUMFs)

Some past U.S. military operations have invoked existing AUMFs—especially the 2001 AUMF against al-Qaeda and associated forces and the 2002 AUMF related to Iraq. These statutes have often served as legal cover for U.S. operations in the Middle East.

However, neither AUMF provides a legally tenable basis for strikes on Iran. Iran was not responsible for the 9/11 attacks, nor was it targeted by the Iraq-related authorization.

The Biden administration did not rely on these authorizations in its formal justification, implicitly acknowledging their irrelevance to the current context. This omission has led many to argue that the President operated outside any clear statutory authority.

D. Executive Practice and Legal Precedents

Presidents have frequently claimed Article II powers to justify limited, short-term uses of force without congressional approval. Notable examples include:

Year	President	Operation	Target	Congressional Approval?
1986	Reagan	Operation El Dorado Canyon	Libya	No
1998	Clinton	Operation Desert Fox	Iraq	No
2011	Obama	Libya Intervention	Gaddafi regime	No
2020	Trump	Killing of Qasem Soleimani	Iran	No
2025	Biden	Strikes on Fordow/Natanz	Iran	No

These precedents reflect a growing trend: presidents acting unilaterally, often citing immediate threats and the need for swift military responses. Yet, each case has been met with legal and political backlash, highlighting the fragile legitimacy of executive war powers absent congressional input.

E. Congressional Reactions and Oversight

In the aftermath of the 2025 operation, several legislators introduced resolutions aimed at reasserting congressional authority. Senator Tim Kaine reintroduced a bill to repeal outdated AUMFs and replace them with a clearer framework for authorizing force. Representatives Khanna and Massie co-sponsored a measure demanding a prohibition on unauthorized war with Iran.

Such reactions underscore the broader institutional struggle over war powers. Though these efforts have yet to result in binding legislation, they reflect a bipartisan consensus that current legal frameworks are insufficient to rein in executive military action.

International Law: UN Charter & Jus ad Bellum

The legality of the June 2025 U.S. strikes on Iran under international law hinges on the rules governing the use of force by states. At the heart of this analysis lie the United Nations Charter and the customary law principle of jus ad bellum, which together establish the legal boundaries for initiating hostilities. The U.S. administration presented the operation as an act of self-defense in response to an imminent threat. However, the absence of United Nations Security Council authorization and the contested factual basis raise serious concerns regarding compliance with international law.

A. Prohibition on the Use of Force: Article 2(4) of the UN Charter

Article 2(4) of the UN Charter prohibits “the threat or use of force against the territorial integrity or political independence of any state.” This principle is considered a cornerstone of the post-World War II international order and part of customary international law. Any military strike by one sovereign state against another is presumed unlawful unless it falls within one of two narrow exceptions:

1. Self-defense under Article 51, or

2. Security Council authorization under Chapter VII.

   
   

In this case, the U.S. did not seek or obtain Security Council approval. No resolution had been passed authorizing the use of force against Iran. Consequently, the U.S. could only justify its actions under the self-defense exception, placing the legal weight entirely on the claim that the strikes were necessary and proportionate.

B. The U.S. Justification: Self-Defense and Imminent Threat

The Biden administration framed the operation as a preemptive act of self-defense, arguing that Iran was accelerating uranium enrichment at Fordow and preparing to mount further attacks against U.S. assets in the region through proxy forces. Officials cited intelligence indicating that missile and drone strikes on U.S. bases in Iraq, Syria, and Jordan were coordinated from Tehran and that additional operations were imminent.

Under Article 51 of the UN Charter, states have the “inherent right of individual or collective self-defense if an armed attack occurs.” However, the U.S. invoked an expanded interpretation of Article 51, based on customary international law, which permits anticipatory self-defense—military action taken to prevent an imminent armed attack.

This interpretation, although frequently cited by Western governments, remains highly contested. The International Court of Justice (ICJ), in the Nicaragua v. United States (1986) and Advisory Opinion on the Legality of the Threat or Use of Nuclear Weapons (1996), took a restrictive view of what constitutes an “armed attack” and did not endorse broad claims of anticipatory self-defense.

For the June 2025 strikes to be lawful under this doctrine, the U.S. must demonstrate:

• A credible and specific threat of an armed attack;

• That the response was necessary (no peaceful alternative); and

• That the use of force was proportionate to the threat.

Legal scholars and UN observers have questioned the sufficiency of the evidence provided. The failure to release detailed intelligence or pursue alternative diplomatic solutions casts doubt on the necessity and proportionality of the operation.

C. Proportionality and Necessity Under Jus ad Bellum

Even if the right of self-defense is accepted, it must comply with two fundamental criteria:

Principle	Legal Requirement	Application to June 2025 Strikes
Necessity	Force must be the only available means to prevent the attack.	U.S. bypassed multilateral diplomatic avenues.
Proportionality	The scale, scope, and effects of force must be limited to what is required to repel the attack.	Use of MOPs on underground facilities was criticized as excessive.

Numerous legal commentators and former UN officials expressed concern that the depth and scale of the attack—targeting high-value, fortified nuclear facilities—resembled an effort to disable Iran’s long-term capabilities rather than to respond to an immediate threat. This interpretation raises the risk that the strikes may be seen not as defensive, but as punitive or strategic, thus exceeding lawful bounds.

D. State Reactions and the Erosion of Legal Norms

Global reactions further underscore the contested legality of the U.S. position. European allies distanced themselves, with the United Kingdom reportedly declining participation due to legal concerns. The UN Secretary-General urged restraint and reaffirmed the importance of adhering to international law.

Iran, for its part, condemned the strikes as a violation of its sovereignty and the UN Charter. Tehran launched retaliatory missile strikes on U.S. facilities in Qatar and Iraq, also invoking the right of self-defense under Article 51. This mutual invocation of self-defense by both parties illustrates the ambiguity and potential for escalation when the boundaries of lawful force are stretched.

The proliferation of unilateral self-defense claims without clear evidentiary thresholds risks eroding the prohibition on the use of force, a foundational principle designed to prevent exactly this kind of cycle of retaliatory violence.

Global Reactions & State Practice

The June 2025 U.S. military strikes on Iranian nuclear facilities prompted swift and polarized responses from governments, international organizations, and legal commentators. These reactions are not only diplomatic in nature—they are also significant from a legal standpoint. How states respond to military actions affects the development of customary international law, particularly under opinio juris and state practice. This section examines the range of global reactions and analyzes their implications for the evolving norms governing the use of force.

A. U.S. and Allied Justifications

In the immediate aftermath of the strikes, the United States issued a formal letter to the United Nations Security Council under Article 51 of the UN Charter. The document cited an “imminent and grave threat” posed by Iran’s nuclear activities and proxy attacks against U.S. personnel and facilities across the Middle East. The Biden administration argued that the operation was both necessary and proportionate to neutralize Iran’s capacity to launch further attacks.

Notably, the United States did not claim an open-ended right to regime change or long-term engagement. Instead, officials emphasized the limited scope of the operation, framing it as a “decisive yet restrained” act of self-defense. However, many U.S. legal scholars questioned whether the threshold for imminence had been satisfied, and whether less extreme measures had been adequately explored.

Among U.S. allies, responses were mixed:

• United Kingdom: Declined to participate in the operation, reportedly due to internal legal advice suggesting the strikes did not meet international law standards. UK Foreign Office officials stressed the need for multilateralism and transparency.

• France and Germany: Expressed concern over escalation and urged restraint, but stopped short of condemning the operation outright. Their statements focused on preventing regional instability and preserving the nuclear non-proliferation regime.

• Israel: Publicly supported the U.S. action, claiming it disrupted Iran’s ability to complete nuclear weapon development. Israeli officials argued the operation aligned with regional self-defense imperatives.

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These varied reactions underscore the absence of consensus among Western powers regarding the legal and strategic legitimacy of the strike.

B. Iranian Response and Right of Self-Defense

Iran condemned the strikes as a violation of its sovereignty and a breach of the United Nations Charter. In an emergency session of the UN General Assembly, Iranian diplomats argued that the attack constituted “armed aggression” under Article 2(4) and demanded international condemnation.

In response, Iran launched ballistic missiles targeting U.S. military installations in Qatar and northern Iraq. The Iranian government issued its own Article 51 notification to the Security Council, invoking its right to self-defense. This mutual reliance on self-defense claims illustrates a central legal challenge: the blurring of lawful and unlawful force when both parties invoke the same legal basis.

Iran’s retaliation was limited in scale, suggesting a strategic choice to avoid full-scale escalation while maintaining its position under international law. However, the risk of further military action has raised alarm in global legal circles over the weakening of norms prohibiting the use of force.

C. United Nations and International Institutions

The United Nations Secretary-General issued a rare public statement calling the situation “deeply alarming,” and urged both parties to immediately return to diplomatic channels. The Security Council convened an emergency meeting, but no resolution condemning the U.S. or Iran was passed due to a deadlock among permanent members.

Meanwhile, the International Atomic Energy Agency (IAEA) expressed concern over the destruction of key monitoring infrastructure at Natanz and Fordow. The IAEA Director-General warned that the operation undermined efforts to verify Iran’s nuclear activities and could erode the integrity of international nuclear agreements.

Legal experts affiliated with the UN Human Rights Council and independent academic bodies also weighed in. The Geneva Academy and the International Commission of Jurists issued statements questioning the proportionality and legal foundation of the U.S. operation, arguing that preventive force without public evidence sets a dangerous precedent.

D. Broader State Practice and Customary Law Trends

The response of the broader international community provides insights into the potential evolution—or erosion—of customary international law. Many states from the Global South, including Brazil, South Africa, and Indonesia, criticized the strikes, labeling them unlawful and destabilizing. These countries reiterated the importance of adhering to UN mechanisms and diplomatic solutions.

By contrast, states in Eastern Europe and parts of Asia remained silent or issued generic calls for de-escalation, avoiding legal judgments. This uneven response reflects a deeper problem: selective enforcement and interpretation of legal norms depending on the actor involved.

Table: Summary of State Positions

State/Institution	Position on Legality	Public Justification
United States	Legal under self-defense	Imminent threat from Iran; Article 51 invoked
United Kingdom	Neutral, did not participate	Legal concerns over proportionality and necessity
Iran	Illegal aggression	Violation of Article 2(4); invoked own self-defense
France & Germany	Cautiously critical	Concerned over escalation, urged diplomacy
Israel	Supportive	Defense against nuclear threat
Russia & China	Strongly critical	Unilateral aggression; risk to global stability
UN Secretary-General	Alarmed	Urged restraint, no legal conclusion offered
IAEA	Concerned	Disruption to verification and inspections

Legal Implications & Future Considerations

The June 2025 U.S. military strikes on Iran present complex legal consequences that extend beyond immediate tactical outcomes. They raise critical questions about constitutional balance in the United States, the durability of international norms on the use of force, and the evolving credibility of multilateral legal institutions. This section evaluates the potential legal implications in both domestic and international spheres, explores the risk of precedent-setting behavior, and outlines future challenges in regulating executive military action.

A. Domestic Legal Challenges and Constitutional Precedent

From a U.S. constitutional perspective, the 2025 strikes amplify long-standing concerns about the erosion of congressional war powers. While the President’s Article II authority provides flexibility to respond to threats, the absence of a clear and immediate attack—and the failure to seek congressional approval—undermine the role of Congress as a co-equal branch with war-declaring authority.

Potential legal consequences may include:

• Congressional inquiries into the legality and intelligence basis of the operation;

• Legislative efforts to repeal outdated Authorizations for Use of Military Force (AUMFs) and tighten restrictions on unilateral executive action;

• Federal litigation, although courts historically defer to the executive on matters of foreign affairs and justiciability.

This incident could catalyze legal reform efforts, especially bipartisan initiatives aimed at restoring congressional oversight. However, unless courts break with past precedent and take a more active role in reviewing war powers disputes, meaningful constitutional rebalancing remains uncertain.

B. International Legal Accountability and Norm Development

At the international level, the operation tests the boundaries of customary international law and the UN Charter’s collective security framework. Iran has publicly indicated its intention to seek recourse at the International Court of Justice (ICJ), arguing that the U.S. violated Article 2(4) of the Charter.

Several possible international legal developments could follow:

• Advisory Opinions from the ICJ or other UN bodies assessing the legality of anticipatory self-defense;

• Diplomatic action within the UN General Assembly under the “Uniting for Peace” mechanism;

• Increased calls for multilateral treaties clarifying the legal definition of imminent threats and proportionality.

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The broader concern lies in precedent formation. If other states adopt similarly broad interpretations of self-defense, international legal norms could degrade, resulting in a de facto permission structure for unilateral military action. This erosion would weaken the Charter’s central promise: that states shall not use force except in narrowly defined circumstances.

C. Strategic Risks of Legal Ambiguity

One of the most pressing concerns is the legal ambiguity surrounding anticipatory self-defense. Without universally accepted criteria for what constitutes an imminent threat, the risk of abuse rises. States could invoke vague threats or classified intelligence to justify preemptive strikes, effectively bypassing legal and diplomatic checks.

This ambiguity creates three primary dangers:

1. Escalation: States that feel unjustly targeted may retaliate violently, claiming reciprocal rights under Article 51.

2. Delegitimization: Repeated exceptions to the use-of-force norm can delegitimize international legal institutions.

3. Legal fragmentation: States may increasingly rely on regional alliances or bilateral security doctrines instead of UN mechanisms, undermining universal applicability.

   
   

These outcomes weaken the rule-based order and make future conflicts more likely to escalate without legal or diplomatic containment.

D. Prospects for War Powers Reform

Within the United States, bipartisan momentum for war powers reform has grown. Lawmakers have reintroduced legislation to:

• Repeal outdated AUMFs, particularly the 2001 and 2002 authorizations;

• Require congressional authorization for any future offensive military operations against nation-states;

• Mandate transparency regarding legal justifications, intelligence assessments, and operational objectives.

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Supporters argue that reform is necessary to restore democratic legitimacy to U.S. military decisions. Opponents contend that requiring legislative pre-approval could hinder timely responses to fast-moving threats. The challenge lies in crafting a legal regime that both constrains overreach and preserves necessary executive flexibility.

E. Recommendations for Legal and Policy Safeguards

To address the legal uncertainty exposed by the June 2025 strikes, several measures could be considered:

Recommendation	Purpose
Codify clear definitions of “imminent threat”	Reduce ambiguity in self-defense claims
Require real-time congressional consultation	Reinforce democratic accountability in war powers
Enhance reporting standards for Article 51 letters	Improve transparency in UN self-defense justifications
Establish multilateral verification mechanisms	Restore trust in intelligence claims that trigger strikes
Encourage judicial review of war powers disputes	Strengthen constitutional checks and legal clarity

These steps would not eliminate geopolitical conflict, but they would reintroduce legal discipline into the decision-making process and reinforce the integrity of the legal system.

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Conclusion

The June 2025 U.S. military strikes on Iran mark a defining moment in the ongoing struggle to clarify the legal boundaries of unilateral uses of force. At the domestic level, the operation reignited constitutional debates over the President’s Article II powers and the enduring relevance of the War Powers Resolution. The absence of congressional authorization exposed the fragility of legislative oversight and the expanding role of executive discretion in matters of war.

Internationally, the strikes raised significant questions under the UN Charter and jus ad bellum. Although framed as an act of anticipatory self-defense, the operation tested the limits of legal justification. The lack of Security Council authorization, disputed claims of imminence, and the scale of the force used drew widespread scrutiny. Many states and institutions warned that legal ambiguity surrounding anticipatory self-defense risks normalizing preemptive war, undermining the international system’s most foundational principles.

The global reactions to the strikes—divided and politically driven—highlight the weakening consensus around the rules governing the use of force. As powerful states increasingly rely on unilateral interpretations of self-defense, international law faces the dual challenge of maintaining credibility and enforcing compliance.

Looking ahead, both U.S. and international legal frameworks require urgent attention. Domestically, war powers reform is essential to recalibrate the balance between executive action and democratic accountability. Globally, there is a pressing need to clarify the thresholds for self-defense under international law and to strengthen multilateral mechanisms for conflict resolution.

Without legal clarity and institutional restraint, the precedent set in June 2025 may erode the rules designed to prevent conflict escalation and unlawful aggression. Preserving the integrity of these legal norms is not simply a legal obligation—it is a strategic necessity for global stability.