The main point here is that neither Israel nor the US can reasonably claim to be exercising their right to self-defence against Iran, pursuant to Article 51 of the Charter, either individually or collectively. Iran did not attack the US or Israel, at least not recently. Whatever threat that any earlier attack may have posed has long dissipated. There was no ongoing armed attack by Iran that could justify resort to force in self-defence. It is therefore only the prevention of some future attack by Iran on the two states, nuclear or otherwise, that could possibly be relevant here, under some theory of anticipatory self-defence in response to an imminent attack. But even on the broadest plausible such theory, a use of force against Iran would be lawful only if (1) Iran had the intent (i.e. its leadership decided) to attack the US/Israel; (2) it had the capability to do so; (3) and it was necessary to use force today, because today would be the last window of opportunity to prevent this future attack.
None of these conditions are met here, just like they weren’t met last summer. If anything, the anticipatory self-defence argument is even weaker today, because the strikes last summer substantially degraded Iran’s capability to build a nuclear weapon – President Trump had even stated that Iran’s nuclear program was ‘obliterated.’ No evidence was presented to show that since last summer somehow Iran reconstituted its programme, had the intent to build a weapon, put it on a ballistic missile, and then use it against the US or Israel. Läs artikel