If only there was some kind of agreed set of conventional rules that could stop this kinda thing... Well since no one is gonna stop them they have no reason to stop. Who knows what else they can get away with? The sky is the limit when it comes to war crimes these days.
The geneva convention is for the weaker countries so the bullies can then point and go "SEE, THEY WARCRIMING". The only way to apply anything to any leader of Russia, the entire country would need to capitulate. And good luck with capitulating Russia, many have tried.
