> An Israeli airstrike carried out within Syria without its consent would be in contravention of Article 2(4) of the United Nations Charter, which prohibits a state from using force against the territorial integrity or political independence of any other state... Unless Israel were able to justify any airstrike as an act of self-defense, it would be in violation of international law.
So... not illegal since hezbollah has been targeting and attacking Israel with Iran's help. Israel is defending itself.
In any case there is no law between sovereign states.
Now, Iran's use of drones to retaliate seems calibrated to avoid a further escalation because it is unlikely that they will cause much damage. But let's see how things unfold as apparently Iran has launched a large number of drones...
Honestly the Israeli response (killing Iranians in a third country) is probably more restrained then the UK would have been. I expect the UK - in a hypothetical world where the Irish had supported the IRA to the degree that Iran supports Hamas/Hezbollah - would have struck Ireland directly and not offered even implausible denials that they had done it but instead trumpeted that fact.
That building in Damascus was obviously used by Iran and Hezbollah as operational or command centre, or similar, since personel from both the Iranian military and Hezbollah were killed in the attack.
Hence it was perfectly "legal", for Israel to destroy it in self-defense.
Do you think it was "legal" for Iran to fire hundreds of drones at Israel's civilian areas (which is what Hamas does as well, btw)? I think that this would be a more obvious breach of "international law" if you wanted to be such a stickler for it...
If American proxies in Guatemala attacked say Cuba, would it be legal for Cuba to retaliate by bombing an American embassy in Mexico? If Cuba did do that, would America be justified in responding by bombing Cuba?