Iraq publicly purchased and was operating a nuclear reactor. Israel didn't have to prove they had one, the whole world knew. Bill Clinton later said that Saddam would have had nukes by 1991 if Israel hadn't done that.
The Sudanese government confirmed that Israeli bombs hit caravans intended to break the Gaza blockade, just as Israel said. Once again, Israel's attacks were against a proven target. (What would Israel gain from striking the Sudanese desert, anyway?)
And the Syrian strikes just happened. Israel hasn't even confirmed their involvement yet. It is entirely possible they have proof, but are waiting until a strategically suitable time to release it.
Anyway, in your scenario, the answer is no, you must present some proof. Especially since forensics experts can tell what was blown up, so if they find nothing dangerous in the bomb site, then the attack is unjustified. Luckily, Israel has yet to do this.