Well there is always bias but that is not just about bias but having an entity above nation state that can provide a ruling on wrong doings. For example, the most powerful nation on earth occupying some country to extract its resources without any entity than can do anything about it, is criminal wrong doing. Yes there is going to be bias but not if they are providing the evidence.

I am not talking about the current ethnic conflict between Israel and Palestinians because that is a century worth of conflict has gone far beyond what courts can rule on. I am talking about USA absolving itself from being accountable in presence of evidence.