The United Kingdom’s Use of Force Against Iran: Walking a Legal Tightrope?

(Aurel Sari – Just Security) On March 1, 2026, British Prime Minister Sir Keir Starmer announced that the United Kingdom is taking defensive military action against Iran. The announcement comes on the heels of his earlier denial that the United Kingdom played any role in the strikes launched by the United States and Israel on Iran on Feb. 28. 2026. These very different statements are underpinned by what appears to be a nuanced legal argument. The purpose of this analysis is to unpack the British position with reference to the rules governing the use of force and the events that have unfolded since Starmer’s initial statement. – The United Kingdom’s Use of Force Against Iran: Walking a Legal Tightrope?