There really isn't one except in cases like with Nazi Germany where there was a clear victor after a militarized war and people who had actually committed the deeds surrendered while alive, so they were put through war crimes trials (or shuffled off to America to build rockets).
In most other cases, the UN and other international lawfare bodies are really only effective against small time criminal warlords who can be arrested by interpol types and even some of them get by with it (KONY). Other than that the UN is about as fucking useless as the league of nations and if any nation decided to just tell them to fuck themselves (and they have many times in the past) they really don't get to do much officially other than whine and cross their arms. Behind the scenes of course they like to arm and fund "rebel" groups. But if Israel or the US wants to say fuck y'all niggas, what are the rest of them going to do? Hell, with as many conflicting treaties as there are in the world, what happens in the inevitable NATO vs BRICS conflict since the major nations behind that are also major forces in the UN?
The entire concept was born out of shortsighted retarded desperation after the world wars and cold war to return to a dream utopia that never even really existed in the first place. Even when the League was in place Japan told them to eat shit and attacked China and America anyway.
