Irans history of agression is well chronicled. The UN has passed umpteen resolutions asking them to comply with UN rules. What should the UN do if they dont? Ask again? At what point will you accept that physical interference is the only solution? Name me one recent conflict solved with diplomacy. Now we have a litteraly smoking gun that Iran is arming Iraqi insurgents with weapons that have killed American soldiers. Thats a pretty clear act of war.