They don't need permission from the state if there are attacks originating from it and Syria are unable or unwilling to do something about it. Do you even international law, bro?
So you're saying that because ISIS in Syria are attacking the Syrian government that it's legal for the US to fly in without permission and launch a bombing campaign despite being asked not to by the country they are bombing? Really? lol.
I suppose that means that because the are attacks originating from Ukraine targeting Ukrainian rebels that would make it nice and legal for Russia to fly in there and start bombing against the will of the Ukrainian government as that's the same thing? No, of course it doesn't.