UN Secretary‑General António Guterres condemned the US‑Israel strikes on Iran on February 28, saying they breached the UN Charter ban on the use of force and posed “a grave threat to international peace and security.” Human rights lawyer Gissou Nia told DW that most international lawyers would see no legal justification for the operation, arguing it violated both international law and US law governing the use of force. Nia also emphasized context: many Iranians have long suffered serious rights abuses and atrocity crimes by their own government, and international law has often failed to deliver remedies for those victims.
The US offered little attempt to ground the operation in international law. President Donald Trump’s January 7, 2026 New York Times remark — ‘I don’t need international law’ — encapsulated that posture. That contrasts with earlier large‑scale conflicts such as the 2003 Iraq invasion, when states at least sought to present legal arguments for their actions.
Self‑defense and the question of imminence
US and Israeli officials framed the strikes as action against Iranian threats, particularly the risk of Iran developing and using a nuclear weapon. Under Article 51 of the UN Charter, the right to use force in self‑defense arises after an armed attack; some jurists permit preemptive action against an ‘imminent’ threat, but that exception is narrow and heavily disputed. Experts say it is unclear whether the claimed Iranian threat met the strict test of imminence required by the UN framework.
Hostile statements by Iranian officials, including threats against Israel, do not by themselves justify preemptive strikes. During the military buildup, US envoy Steve Witkoff warned Iran was ‘probably a week away’ from producing industrial‑grade bomb‑making material — a claim that appears inconsistent with President Trump’s earlier assertion after the 2025 bombing that Iran’s nuclear facilities had been obliterated.
Killing a head of state: assassination or lawful targeting?
The death of Iran’s supreme leader, Ayatollah Ali Khamenei, in the strikes raises acute legal questions. In a declared international armed conflict, combatants can be lawful targets, but the deliberate killing of a political leader is widely regarded as assassination if the initial use of force cannot be justified under the UN Charter. Nia noted the moral and legal complexity: some Iranians regarded Khamenei as responsible for mass harm and welcomed his death, while others would have preferred judicial proceedings and transparent accountability.
US domestic law also expressly forbids assassinations. Executive Order 12333, signed in 1976, states that US government employees shall not engage in or conspire to engage in assassination. Legal scholars say that prohibition has been eroded in practice, with some actions recharacterized as self‑defense. Analysts point to precedents such as the 1986 strike on Libyan leader Muammar Gaddafi and argue that the Trump administration’s public claiming of responsibility for Khamenei’s death marks a significant break with past restraint.
Iran’s right to retaliate and the limits on response
Iran launched missiles and drones at Israel and at US bases across the Gulf after the strikes. International law allows a state that has suffered an armed attack to respond in self‑defense, but the legality of any response depends on its targets, necessity and proportionality. Deliberate attacks on civilians breach international humanitarian law. Strikes that spread into third countries hosting US forces risk violating the prohibition on attacking states not party to the initial aggression; commentators described some of Iran’s actions as ‘misdirected self‑defense.’
Reports suggested projectiles or debris believed to be Iranian struck sites in Bahrain, Qatar, the UAE, Israel, the Palestinian territories, Kuwait, Jordan, Saudi Arabia, Oman and Cyprus, raising legal questions where civilian infrastructure or neutral third states were affected.
Allied and global reactions
European governments largely responded cautiously, often avoiding direct condemnation of the US and Israel while warning against escalation. German Chancellor Friedrich Merz warned that established rules, including international law, were being ‘observed less and less,’ while saying it was not the moment to lecture allies. German Foreign Minister Johann Wadephul spoke of ‘significant questions’ about legal classification, and European Commission President Ursula von der Leyen described the developments as ‘greatly concerning,’ urging protection of civilians and respect for international law.
Outside Europe reactions were mixed: close partners such as Australia and Canada expressed support for the US, while others stayed at arm’s length. Russia and China criticized the US‑Israeli operation; Russia said it stood ready to help advance peaceful solutions grounded in international law.
Does this episode signal a weakening of international law?
Legal experts and political scientists warn the crisis could mark a turning point. If powerful states increasingly rely on unilateral strikes and expansive claims of self‑defense, the legal rules meant to limit resort to force may erode. Political scientist Luca Trenta argues the Trump administration has shown little interest in legal justification for military actions, and that public attribution of targeted killings could normalize such practices internationally.
The immediate legal judgment depends on whether the US‑Israeli strikes satisfied the narrow self‑defense threshold (including imminence), whether they met necessity and proportionality requirements, and whether Iran’s counterstrikes complied with limits on targeting civilians and third parties. Given disputed claims about imminence, the legal sensitivities of killing a head of state, and the regional spread of violence, many international lawyers conclude there is no clear legal justification for the attacks — a view echoed by the UN Secretary‑General. Political dynamics, power imbalances and uneven enforcement of international law make meaningful legal accountability uncertain.
Edited by Andreas Illmer