Iran strikes: 'US cannot rely on self-defence claims'

Professor Michael Schmitt is an expert in international law rules governing warfare at the School of Law, University of Reading.

Days before the joint US-Israel attack on Iran, he wrote a detailed analysis of the legal basis on which US military action could be taken (with colleagues Tess Bridgeman and Ryan Goodman at New York University School of Law).

Highlighting this analysis, Professor Schmitt said:

"Under international law, the United States lacks any lawful basis to use force against Iran.

"The UN Charter establishes a clear prohibition on the use of force, and nothing in the circumstances that existed prior to the US and Israeli raids on Saturday fits within the narrow exceptions to that rule.

"Claims of humanitarian intervention do not withstand scrutiny. Even if one were to accept the controversial notion that humanitarian intervention is a valid legal doctrine, it applies only where the primary and genuine purpose is to halt large‑scale human suffering. The shifting justification of US threats, from protest‑related abuses to nuclear negotiations, makes clear that such motives are, at best, questionable.

"The United States cannot rely on claims of self‑defence. Before Saturday's raids, Iran possessed no nuclear weapons, showed no intent to attack, and negotiations over its nuclear programme were actively ongoing. Without evidence of an imminent armed attack, anticipatory self‑defence simply does not apply. Nor can the United States invoke the defence of Israel. While Iran demonstrates frequent hostility towards Israel, there was no basis for Israel itself to claim an imminent attack by Iran, and therefore no foundation for collective self‑defence.

"This is also relevant to other states involved in the conflict. States such as the United Kingdom are legally barred from assisting an unlawful use of force. While subsequent statements from the UK government about supporting US actions have focused on actions to prevent civilian casualties, such as drone attacks on Dubai, allowing strikes to be launched from British territory or airbases would have made the UK complicit, under the law of State responsibility.

"Even if Iran were to now accept a deal on its nuclear ambitions or long-range missiles under the weight of threats or military action, those agreements could be void under the Vienna Convention on the Law of Treaties.

"The US Administration has shown through repeated actions directing military force that its policies and practices are incompatible with the most fundamental rules governing international peace and security, rules designed to avoid another world war and which have operated for more than 80 years."