Even a resolution of the UN security council means nothing.
I wasn't talking about international law. Israel is willing to go to the mat on this, and apparently convinced this is a life-or-death issue. A lot of other countries, including the only superpower, NATO and the EU agree or at the very least don't want to let Israel be destroyed if Israel chose to stop Iran's nuclear program. As far as international consensus goes, that's pretty strong.
"Aggression" is quite an arbitrary definition. Iran has threatened Israel with annihilation for decades, and occasionally they tried. They do/did have a nuclear program, they certainly have chemical weapons. They keep attacking shipping and causing further armed conflict around the region...
"International Law", which today mainly consists of Russia and China sabotaging everyone else, is not going to stop Israel from defending itself.