Some legal scholars have suggested a more justifiable characterization for the U.S. actions here may be as a response to past Iranian military attacks, not an imminent one. And in a letter to the United Nations defending the attack, U.S. Ambassador Kelly Craft suggested that Iran’s past actions justify the U.S. strike. “Over the past several months, the United States has been the target of a series of escalating threats and armed attacks by the Islamic Republic of Iran,” she wrote — including the shooting down of a U.S. drone in June, and a “series of attacks” by “Qods Force-backed” militias. Even were each of the acts listed in the letter both attributable to Iran and properly characterized as armed attacks — a stretch for various reasons, including that the U.S. drone was itself unmanned and that Iran claimed it shot it down in Iranian airspace — the use of force in response must still be necessary to stop an ongoing attack or prevent one. Soleimani’s history, and Iran’s, provide context for analyzing the nature of any current threat. But the use of force as retaliation or punishment for a past wrong is strictly prohibited under international law; the narrow exceptions the charter permits do not include revenge. So we are back to the original question: whether Soleimani posed an immediate threat for which the use of force was necessary.
Finally, even were an attack against Iran itself justified, the fact that the Soleimani strike took place in Iraq makes the question of imminence even more important. Iraq, of course, did not itself attack us.