Operation Epic Fury and International Law, What the Rules of War Actually Say

Was Operation Epic Fury legal under international law?

Operation Epic Fury — the coordinated U.S.-Israeli strikes on Iran launched February 28, 2026 — sits at the center of an active international law dispute. The U.S. government argues the strikes were lawful acts of self-defense under Article 51 of the UN Charter. More than 100 international law experts, the Carnegie Endowment, and the Center for International Policy argue they were not — and that the strikes violated the Charter’s core prohibition on the use of force against another state.

On February 28, 2026, the United States and Israel launched coordinated military operations against Iran. The operation came two days after the most substantive round of U.S.-Iran nuclear negotiations in years had concluded in Geneva, with both parties agreeing to continue talks. Within hours of those assurances, the bombs fell. Iran’s Supreme Leader Ayatollah Ali Khamenei was killed in the first hours. Strikes hit military infrastructure across multiple Iranian cities.

What followed was a legal argument that is still playing out — in letters to the UN Security Council, in briefs filed by law professors, in congressional hearings, and in the State Department’s own published legal defense of the operation, released on April 22, 2026.

This article explains the international law framework that applies, what each side argues, what happened at the Minab school, and what — if anything — international law can actually do about it. For the domestic U.S. legal dimension — the War Powers Resolution and the 60-day clock — read our companion article War Powers Resolution Explained: The 60-Day Rule — allaboutlawyer.com.

The Two-Layer Legal Framework: Jus ad Bellum and Jus in Bello

International law evaluates armed conflict on two separate tracks. Understanding the difference is essential to following this debate.

Jus ad bellum — Latin for “law to war” — governs the decision to use military force in the first place. It asks: did the state have a legal right to start fighting? This is primarily governed by the UN Charter, which the United States ratified in 1945 and which is binding on it as a treaty.

Jus in bello — Latin for “law in war” — governs how a conflict is conducted once it begins. It asks: did the parties follow the rules once the fighting started? This is governed by the Geneva Conventions, their Additional Protocols, and customary international humanitarian law — what military lawyers call the Law of Armed Conflict (LOAC).

Legal experts have raised concerns about both dimensions: jus ad bellum, or the decision to go to war; and jus in bello, or the conduct of hostilities, including the Minab school strike and the broader pattern of strikes on civilian infrastructure. The U.S. government’s April 22 State Department memo addresses primarily the jus ad bellum question — whether the decision to strike was lawful. Critics argue both questions deserve serious scrutiny.

The UN Charter Rules: What Makes a Strike Legal or Illegal?

The UN Charter establishes a general ban on the threat or use of force against the territorial integrity or political independence of any state. This rule is widely recognised as a cornerstone of contemporary international law and reflects both treaty and customary norms. It lives in Article 2(4).

Any cross-border military strike constitutes a prima facie breach of Article 2(4). Aerial bombardment, missile launches, and coordinated military operations directed at the territory of another sovereign state fall squarely within the ordinary meaning of “use of force.” The fact that the targets were military rather than civilian does not remove the conduct from the scope of the prohibition. The Charter regulates the resort to force, not merely its humanitarian consequences.

There are three narrow exceptions under which a strike can be lawful despite Article 2(4):

Exception 1 — UN Security Council Authorization. The Security Council can authorize member states to use force under Chapter VII of the Charter. The Security Council did not authorize the attack on Iran. The U.S. and UK hold vetoes on the Security Council and neither sought authorization.

Exception 2 — Individual Self-Defense under Article 51. A state may use force in response to an actual or imminent armed attack against it. The attack must be real, not speculative. The response must be necessary and proportionate.

Exception 3 — Collective Self-Defense under Article 51. A state may use force on behalf of an ally that has suffered or faces an imminent armed attack — if that ally requests the assistance. This is the primary legal theory the U.S. has advanced for Operation Epic Fury.

Related article: Slang for Law Enforcement, 60+ Terms, Their Origins, and What They Actually Mean

The U.S. Government’s Legal Argument

On April 22, 2026, the U.S. State Department’s Office of the Legal Adviser published a formal legal defense of Operation Epic Fury — an unusual step that signals the administration recognized the international legal pressure it faces.

The United States argued it is engaged in this conflict at the request of and in the collective self-defense of its Israeli ally, as well as in the exercise of the United States’ own inherent right of self-defense. The administration has explained its position in multiple letters to the U.N. Security Council, including on March 10.

The administration’s legal theory rests on three claims. First, that Iran has been engaged in an ongoing armed conflict with Israel and the United States through direct and proxy attacks since at least 2019, meaning February 28 was not the start of a new war but a continuation of an existing one. Second, that a state in an ongoing armed conflict does not need to demonstrate that each individual use of force responds to a specific, imminent attack — the conflict’s continuation is sufficient legal basis for continued operations. Third, that Iran’s nuclear weapons program posed a threat that could not legally be required to wait until a missile was ready to launch.

The State Department stated: “The inherent right to self-defense cannot rationally be construed to require a State to wait until a self-avowedly hostile actor has a nuclear warhead-tipped missile ready to launch before lawfully taking a disabling strike. Hesitation under these circumstances would render self-defense futile.”

The administration also argued that the ceasefire period between June 2025 and February 2026 did not end the underlying armed conflict, because the parties made no unilateral declarations of war’s end and continued to plan for military engagement if diplomacy failed.

The Critics’ Legal Argument

More than 100 international law experts — including professors from Stanford, Yale, American University, and Rutgers — signed an open letter challenging the operation’s legality. The Carnegie Endowment for International Peace and the Center for International Policy published detailed legal analyses reaching the same conclusion.

The experts argued the strikes launched by the United States and Israel on February 28, 2026 clearly violated the United Nations Charter prohibition on the use of force. Force against another state is only permitted in self-defense against an actual or imminent armed attack or where authorized by the UN Security Council. Despite the Trump administration’s varied and sometimes conflicting claims, there is no evidence that Iran posed an imminent threat that could justify the use of force.

Critics argue the U.S. has failed to show that either Israel or the United States suffered an armed attack by Iran — which is necessary under international law to justify the use of force in self-defense. The administration’s claim of an ongoing armed conflict is characterized as a legal misdirection that does not satisfy the jus ad bellum requirement of a prior armed attack or threat of imminent armed attack.

On the question of diplomacy, critics note it is not plausible to argue the administration had exhausted diplomatic options. The Trump administration’s 2025 negotiations with Iran were terminated not because they were futile, but due to Israel’s surprise attack on Iran in the midst of the talks. The February 2026 negotiations, according to Omani mediators, had not reached a dead end before the strikes began.

Carnegie’s legal analysis found that given there were no active hostilities between the United States and Iran prior to the launch of Operation Epic Fury, the assertion that the strikes were justifiable as part of an ongoing armed conflict is “patently wrong also as a matter of fact.”

The Minab School Strike: A Separate Legal Question

Whatever one concludes about jus ad bellum — whether the decision to fight was lawful — a second and separate legal question exists: how was the conflict conducted once it began?

On February 28, 2026, the Shajareh Tayyebeh Elementary School in Minab, Iran was struck. 156 civilians were killed, including 120 schoolchildren. As of March 15, 2026, the attack was the deadliest strike in terms of civilian casualties in the ongoing war.

Multiple independent investigations concluded that the United States was responsible for the strike. Amnesty International’s analysis of audiovisual evidence and missile remnants indicated that a U.S.-manufactured Tomahawk cruise missile was likely used. Tomahawk missiles are used exclusively by U.S. and allied naval forces.

President Trump denied U.S. responsibility, falsely stating that “It was done by Iran.” However, a preliminary investigation by the Department of Defense reportedly determined that the U.S. conducted the strike, and that the targeting had been based on outdated intelligence.

Under international humanitarian law — specifically Article 51(5)(b) of Additional Protocol I to the Geneva Conventions — attacks are prohibited when they are expected to cause civilian casualties excessive in relation to the concrete and direct military advantage anticipated. Civilian objects like schools are protected unless they are being used for military purposes.

Legal analysts at Lawfare concluded that even framing the attack as a mistake does not excuse responsibility. If U.S. forces failed to take the necessary measures to avoid civilian casualties — including maintaining updated “no strike” lists — they could be considered in violation of international humanitarian law. If individuals acted sufficiently recklessly, they may be guilty of a war crime under the ICRC’s Customary International Humanitarian Law Study, which requires that war crimes be committed willfully — either intentionally or recklessly.

120 members of Congress, led by Representative Jason Crow, demanded the Pentagon answer whether the U.S. conducted the strike, what the assessed civilian harm risk was, and whether artificial intelligence was used in the targeting process. The Pentagon’s investigation has not been made public as of April 26, 2026.

The Minab strike is far from the only reported strike on civilian sites. U.S. and Israeli attacks have reportedly struck other schools, multiple medical facilities, numerous residential areas, and a water desalination plant — all of which are protected under international humanitarian law, raising what Refugees International called “the serious prospect that these strikes could constitute war crimes.”

What Has Made Enforcement of International Law Harder

Two institutional developments — one at the U.S. government level and one at the international level — have weakened the mechanisms that might otherwise constrain conduct.

Since taking office, Secretary Pete Hegseth has closed the Pentagon office tasked with avoiding civilian harm and fired the leadership of the Judge Advocate General corps, tilting the corps toward a more lenient posture toward targeting and oversight. The Civilian Protection Center of Excellence — created by Congress to increase transparency and accountability for civilian harm — was significantly reduced before the Iran operation began.

At the international level, an ICJ finding of illegality would produce a legal record of the violation but would be unenforceable. As Nicaragua v. United States demonstrated in 1986, a favorable ICJ judgment is unenforceable when the respondent holds a Security Council veto. The United States holds a permanent veto on the Security Council, making binding enforcement through the Council impossible.

The UN General Assembly, through its Uniting for Peace procedure, can convene emergency special sessions and pass resolutions characterizing uses of force — but those resolutions carry normative weight only, not binding force.

What Happens Next Legally

The State Department’s April 22 memo is not the end of this legal argument — it is the opening of a formal record. Critics will continue to respond. Academic institutions and NGOs will publish legal assessments. Congressional investigations into the Minab strike may produce public findings.

Critics note that if the United States had been engaged in an ongoing armed conflict with Iran since at least June 2025, then the Trump administration would be using military force in violation not only of the U.S. Constitution but also of the War Powers Resolution — whose 60-day clock would have long expired for any 2025 operations. That argument ties the international law question directly back to the domestic constitutional question still unresolved in Congress. Presidential War Powers: What the Constitution Actually Says — allaboutlawyer.com

Frequently Asked Questions

Q: What is the legal deadline for challenging international law violations from Operation Epic Fury? 

 International law does not have a statute of limitations for war crimes in the traditional legal sense. The International Criminal Court has jurisdiction over war crimes committed on the territory of member states or by nationals of member states — but the United States is not an ICC member. Referrals to the International Court of Justice can be made by states at any time and are not time-barred, but are subject to the court’s jurisdiction, which the U.S. can contest. Claims under international humanitarian law — including reparations demands — also do not expire, though enforcement depends on political will and institutional capacity.

Q: How long could legal proceedings related to Operation Epic Fury take?

 Practically speaking, legal accountability for military operations of this scale unfolds over years or decades — if it comes at all. The Pentagon’s internal investigation into the Minab school strike is ongoing and has no announced timeline for public release. Congressional oversight hearings could produce findings within months. ICJ proceedings typically take years to reach a merits judgment. The political and legal record being built now — through State Department memos, expert letters, NGO reports, and congressional demands — forms the evidentiary foundation for any future proceedings.

Q: Do I need a lawyer to understand my rights related to this conflict? 

 International humanitarian law creates rights for affected civilians — including rights to reparation and compensation for unlawful harm — but enforcing those rights is extremely difficult when the responsible state is a permanent UN Security Council member. If you are a legal researcher, journalist, advocacy organization, or government official working on these issues, an international law attorney specializing in the law of armed conflict is the right resource. For private individuals, organizations like the International Committee of the Red Cross and Amnesty International track civilian harm documentation and can direct victims’ families to available legal channels.

Q: What is Article 51 of the UN Charter, and does it apply here? 

 Article 51 preserves a state’s “inherent right of individual or collective self-defense if an armed attack occurs” against it. The U.S. invokes Article 51 collective self-defense — arguing it acted at Israel’s request in response to Iran’s sustained aggression. Critics argue Article 51 requires a prior armed attack of sufficient gravity, and that the U.S. and Israel have not demonstrated Iran posed an imminent attack that triggered that right in February 2026. The legal dispute centers precisely on whether the facts satisfy Article 51’s requirements.

Q: Could U.S. military personnel face war crimes prosecution over the Minab school strike?

 As a practical matter, prosecution before the International Criminal Court is not available because the United States is not an ICC member state. Prosecution before U.S. military courts — courts-martial — is possible if the Pentagon’s investigation finds evidence of criminal recklessness or intent. Lawfare’s legal analysis concluded that if military personnel failed to take required precautions — such as maintaining updated no-strike lists — and if that failure was sufficiently reckless, it could meet the war crimes threshold under international humanitarian law. No charges have been filed. The Pentagon’s investigation has not been made public.

Q: What did the State Department actually say about Operation Epic Fury’s legality?

 On April 22, 2026, the State Department’s Office of the Legal Adviser published a formal memorandum arguing the operation was lawful under international law. The core argument is that the United States is engaged in an ongoing international armed conflict with Iran — predating February 2026 — and that it is acting in collective self-defense of Israel at Israel’s request, as well as in the exercise of its own inherent right of self-defense. Critics, including former State Department lawyers, have called the memo’s legal reasoning “defective and overly permissive.”

Legal Terms Used in This Article

Jus ad bellum: The body of international law governing when a state may lawfully resort to armed force. Primarily codified in the UN Charter, it prohibits the use of force except in self-defense or with Security Council authorization.

Jus in bello: The body of international law governing how armed conflict must be conducted once it begins — regardless of whether the initial decision to fight was lawful. Codified in the Geneva Conventions and their Additional Protocols, it requires parties to distinguish between combatants and civilians and prohibits disproportionate harm to civilians.

Article 2(4) of the UN Charter: The foundational prohibition on the use of force against another state’s territorial integrity or political independence. Every cross-border military strike engages this provision and must be justified under one of the Charter’s narrow exceptions.

Article 51 of the UN Charter: The provision preserving a state’s inherent right of individual and collective self-defense against an armed attack. Requires a prior armed attack — or imminent armed attack — and that the response be necessary and proportionate.

Proportionality (IHL): The rule under international humanitarian law that an attack must not cause civilian harm excessive in relation to the concrete and direct military advantage anticipated. A strike on a school killing 156 civilians raises serious proportionality questions even if the target was a nearby military facility.

Distinction: The fundamental IHL rule requiring parties to armed conflict to distinguish at all times between civilians and combatants, and between civilian objects and military objectives. Civilian objects like schools, hospitals, and water infrastructure are protected from attack.

Customary international law: Rules binding on all states regardless of whether they have signed a specific treaty, because the rules reflect consistent state practice accepted as legally required. The prohibition on the use of force and the core rules of IHL are binding as customary law in addition to treaty law.

ICC (International Criminal Court): The permanent international tribunal with jurisdiction to prosecute individuals for war crimes, crimes against humanity, and genocide. The United States is not a member state, which significantly limits the ICC’s practical jurisdiction over U.S. personnel.

Conclusion

Operation Epic Fury has produced two simultaneous legal disputes — one about whether the strikes should have happened at all under jus ad bellum, and one about how they were conducted under jus in bello. The U.S. government has published a formal legal defense. Over 100 international law experts have published a formal rebuttal. The Minab school investigation remains incomplete and unpublished.

What is clear is that this conflict is testing the limits of the international legal framework in ways that will shape how states — not just the United States — understand their rights to use force for years to come. The legal record being built now, in letters, memos, expert briefs, and congressional demands, matters regardless of whether enforcement follows.

Visit AllAboutLawyer.com to read our full analysis of the War Powers Resolution’s 60-day deadline, what the Constitution says about presidential war powers, and what Congress can legally do next. War Powers Resolution Explained: The 60-Day Rule — allaboutlawyer.com

Disclaimer: This article is for informational purposes only and does not constitute legal advice. International law involves contested legal and factual judgments on which credentialed experts disagree. All allegations about specific incidents reflect reporting and expert analysis available as of April 26, 2026, not legal findings. For advice regarding your specific situation, consult a licensed attorney.

Sources: U.S. Department of State, Office of the Legal Adviser — Operation Epic Fury and International Law (April 22, 2026); Just Security — Brian Finucane analysis (April 24, 2026); Just Security — 100+ Law Professors Letter (April 2026); Carnegie Endowment for International Peace — Operation Epic Fury and the International Law on the Use of Force (March 2026); Center for International Policy — Operation Epic Fury, Regime Change, and the Collapse of Legal Constraint (March 2026); Lawfare — Was the Attack on an Iranian Primary School a War Crime? (April 2026); Amnesty International USA — Minab School Strike Statement (March 2026); Refugees International — Civilian Harm Report (March 2026); Representative Jason Crow press release (March 2026); Washington Times — Iran demands Arab compensation (April 2026); UN Charter, Articles 2(4) and 51; Geneva Conventions Additional Protocol I, Article 51(5)(b). Last Updated: April 26, 2026