there are a couple of problems with these "international organisations": first and foremost - they are created by the few former colonial powers who were never hold accountable for their own war crimes - but instead gave them the additional power to judge over their former victims (and the rest of the world).
the second point is - these organisations are used to cement the status quo - which is also created by the colonial powers and has absolutely nothing to do with the reality in the world - thus on one hand making all conflicts unavoidable and on the other hand mostly illegal.
the third point is - the rules are not applied to all countries in the same way - e.g. Turkey occupied half of Cyprus and displaced a large part of its population, Turkey is bombing innocent people in Syria, Turkey keeps refugees that originally headed to Europe under very inhuman conditions - not only there are no sanctions for that, Europe is basically funding all of this. As Russia occupied Georgia and annexed parts of it, there were no investigations, no sanctions, nothing. As China occupied Tibet, there were no sanctions but huge investments instead. And there are many more examples.
If you want to have an accepted legal system then it may not be biased and has to apply to everyone without exceptions - what we have at the moment is not even a joke. It's the opposite of a legal system.