UN Secretary‑General António Guterres condemned the US‑Israel offensive against Iran on February 28, saying the strikes violated the UN Charter’s ban on the use of force and posed “a grave threat to international peace and security.” Human rights lawyer Gissou Nia told DW most international lawyers would agree there is no legal justification for the attack and that it violated both international law and US law on the use of force. Nia also noted the wider context: many Iranians have suffered serious rights violations and atrocity crimes by their regime over decades, and international law has often failed to provide them redress.
The US government has given little sign it is trying to justify the operation under international law. President Donald Trump’s remark in a January 7, 2026 New York Times interview — “I don’t need international law” — captured that stance. This contrasts with past conflicts, such as the 2003 Iraq invasion, when governments at least tried to frame actions in legal terms.
Self‑defense and imminence
US and Israeli officials have argued they acted against Iranian threats, particularly the danger of Iran producing and using a nuclear weapon. Under Article 51 of the UN Charter, states may use force in self‑defense only after an armed attack; some jurists allow force against an “imminent threat,” but that interpretation is highly contested. Experts say it is unclear whether the claimed Iranian threats were immediate enough to meet the UN’s strict self‑defense rules.
Iran’s officials have repeatedly made hostile statements toward Israel, including threats to “destroy” it, but experts underline that rhetoric alone does not make preemptive force lawful. 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 at odds with President Trump’s earlier statement after the 2025 bombing that Iran’s nuclear facilities had been obliterated.
Killing of a head of state: assassination or lawful targeting?
The killing of Iran’s supreme leader, Ayatollah Ali Khamenei, in the strikes is legally sensitive. While combatants are legitimate targets in an armed conflict, the intentional killing of a political leader is widely viewed as assassination if the use of force itself cannot be justified under the UN Charter. Nia acknowledged the moral and legal complexity: many Iranians saw Khamenei as responsible for mass deaths and some welcomed his death, while others would have preferred legal accountability in court.
US domestic law also bans assassinations. Executive Order 12333, first signed in 1976, states that no US government employee shall engage in or conspire to engage in assassination. Legal scholars say this prohibition has been eroded over time, with US policy treating some actions as permissible if framed as self‑defense. Luca Trenta, a political scientist at Swansea University, noted past precedence such as the 1986 strike on Libyan leader Muammar Gaddafi and argued that the Trump administration’s public taking of credit for Khamenei’s killing marks a significant departure.
Iran’s right to respond, and the limits of retaliation
Iran launched missiles and drones at Israel and US bases across the Gulf after the strikes. Under international law, a state that suffers an armed attack may respond in self‑defense. But the legality of Iran’s retaliation depends on its targets and proportionality. Attacks on civilian sites — including in Israel and Dubai — violate international humanitarian law, which bans deliberate targeting of civilians. Strikes that extended to third countries hosting US forces risk breaching the prohibition on attacking states not party to the initial attack; analysts described some actions as “misdirected self‑defense.”
Reports indicate missiles or drones believed to be from Iran struck locations across the region — Bahrain, Qatar, the UAE, Israel, the Palestinian territories, Kuwait, Jordan, Saudi Arabia, Oman, and Cyprus — raising legal questions where civilian infrastructure or third‑party states were affected.
Allied and global reactions
European governments largely reacted cautiously. Many avoided directly criticizing the US and Israel while expressing concern about a wider regional war. German Chancellor Friedrich Merz warned that existing rules, including international law, are being “observed less and less,” but added it was not the moment to lecture allies. German Foreign Minister Johann Wadephul said there are “significant questions” and doubts about legal classification, while also noting the threat Iran poses. European Commission President Ursula von der Leyen called the developments “greatly concerning,” stressing the need to protect civilians and respect international law.
Beyond Europe, reactions were mixed: close partners such as Australia and Canada expressed support for the US, while others kept their distance. Russia and China criticized the US‑Israeli operation; Russia said it stood ready to assist in advancing peaceful solutions grounded in international law.
Does this signal a weakening of international law?
Legal experts and political scientists warn the conflict could mark a turning point. As powerful states rely more on unilateral strikes and broad claims of self‑defense, the rules designed to prevent war may erode. Trenta argued that the Trump administration has shown little interest in justifying military actions under international law, citing past operations where legal constraints were largely ignored. He warned this could herald a normalization of targeted killings at the international level, with other states possibly following suit.
The immediate legal assessment hinges on whether the US‑Israeli strikes met the strict requirements for self‑defense and whether they observed principles of necessity and proportionality, and on whether Iran’s responses complied with limits on targeting civilians and third states. Given contested claims about imminence, the killing of a head of state, and the regional spread of violence, many international lawyers conclude there is no clear legal justification for the attacks — a position echoed by the UN Secretary‑General — while political dynamics and uneven enforcement of international law complicate prospects for legal accountability.
Edited by: Andreas Illmer