AI (06.03.2026) – ‘As of early March 2026, many international legal experts, human rights organizations, and some UN officials have characterised the ongoing military operations by the United States and Israel against Iran as an illegal war of aggression.
The core of the legal dispute hinges on whether the strikes meet the strict criteria for lawful force under the United Nations Charter.
Arguments for Illegality
Under international law, the use of force is only permitted in two scenarios: self-defence against an “armed attack” or authorization by the UN Security Council.
- Lack of Authorization: The UN Security Council has not authorised military action against Iran, and the US has not requested such authorization.
- Absence of “Armed Attack”: Critics, including UN Special Rapporteur Ben Saul, argue that Iran had not launched an armed attack against the US or Israel prior to the strikes.
- Failure of “Imminence”: For “pre-emptive” self-defence to be legal under the Caroline Doctrine, a threat must be “instant, overwhelming, leaving no choice of means, and no moment for deliberation”. Experts state a weeks-long military buildup and ongoing diplomatic talks disqualify this justification.
- War of Aggression: Organizations like DAWN have called for the strikes to be investigated as a “crime of aggression,” defined by UN Resolution 3314 as the use of armed force against the sovereignty of another state without legal justification.
Arguments for Legality/Justification
The US and Israel justify the campaign as a necessary defensive measure:
- Preventive Defence: They argue the strikes are necessary to prevent Iran from acquiring nuclear weapons and to counter its support for regional proxy groups.
- Ongoing Armed Conflict: Some legal scholars suggest the strikes are a continuation of a long-standing, undeclared war in which Iran has already initiated hostilities through its proxies.
- Moral Justification: Proponents argue that the removal of a “bloodthirsty” regime and the protection of regional peace provide a moral basis for action, even if the formal legal framework is strained.
Domestic Legal Concerns (US)
The war is also being challenged under US law. Critics and some members of Congress argue the strikes violate the War Powers Resolution of 1973, as President Trump bypassed the required congressional authorization for offensive operations. …
The joint US-Israeli military strikes on Iran, launched on 28 February 2026, have been widely criticised by international law experts as failing to meet the legal requirements of the Caroline principles.
The Caroline doctrine is the standard for “anticipatory self-defence” in customary international law. It requires that the necessity for self-defence be “instant, overwhelming, leaving no choice of means, and no moment for deliberation“.
Experts argue the 2026 strikes failed this test for several reasons:
- Lack of Imminence: There was no evidence of an “instant” or “imminent” armed attack from Iran. US intelligence as recently as March 2025 had judged that Iran was not building a nuclear weapon.
- Available Alternatives: The attacks occurred while active diplomatic negotiations were underway. An Omani mediator had described a “breakthrough” just one day before the strikes began.
- Deliberate Planning: The strikes were preceded by a weeks-long military buildup and months of tactical planning, which contradicts the “no moment for deliberation” requirement.
Competing Arguments
- Official US/Israeli Position: The Trump administration and Israel justified the action as a “pre-emptive attack” to eliminate an “existential threat” and prevent Iran from rebuilding its nuclear program. They cited Iran’s long-term support for proxies and alleged nuclear ambitions as a continuous threat.
- “Ongoing Conflict” Argument: Some supporters argue the strikes are part of an ongoing armed conflict started by Iran years ago, rather than a new act of aggression.
- International Consensus: Most international legal scholars, as well as the UN Secretary-General, have termed the strikes a violation of Article 2(4) of the UN Charter, which prohibits the use of force against another sovereign state. …
Based on reports from early March 2026, multiple Yale Law School professors and legal experts have argued that U.S. and Israeli military strikes on Iran are illegal under both domestic and international law.
Yale Daily News +1Here are the key arguments and individuals involved:
- Harold Hongju Koh: The Sterling Professor of International Law at Yale Law School and former State Department legal adviser stated that strikes on Iran constitute a “war of choice that is unlawful under both US and international law”. Koh argued that the actions violate the UN Charter because they were not taken in legitimate self-defense.
- Oona Hathaway: A Yale Law School professor of international law has described the strikes as “blatantly illegal,” arguing that they violate international laws regarding the use of force.
- Eugene Fidell: A senior research scholar at Yale Law School has repeatedly characterized the actions as a constitutional breach, noting that the strikes occurred without necessary Congressional authorization.
- Context of the Legal Argument: The arguments center on the idea that the U.S. strikes violate the UN Charter’s prohibition on the use of force, as there was no direct, imminent threat from Iran that justified the action. Yale Daily News +4
These professors argue that such actions disregard the post-WWII international legal order, which restricts the use of force to scenarios involving self-defense or UN Security Council authorization.’
See also:
US & Israel Launch ILLEGAL War on Iran