I have always been rather skeptic towards the ICC, the ICTY and other efforts for international criminal justice. I believe in the primacy of politics whose job it is to guarantee peace and to provide the rules for inter-human behavior.
One claim of the international lawyers was that it would help to establish facts and so to prevent future disputes. The Nuremberg Trials didn't completely prevent Holocaust denial but they at least limited the damage - is the reasoning. But those trials also showed the arbitrariness of those rules. For example the bombing of (civilian) Rotterdam and London could not be proclaimed a crime because the Allies later on had done much larger scale bombings of German cities.
We see the same now with former Yugoslavia. In Slovenia - that started the violence and by doing so set the pattern for the rest - no one was even indicted. Croatia drove out some 400,000 Serbs and killed many hundreds of them - but again no one was convicted. In the end the only non-Serbs convicted of war crimes were Croats attacking Muslims.
Regarding politics the ICTY was just as bad. By sticking to the "Great Serbia" myth it evaded any realistic discussion about how politics in Croatia and Bosnia had derailed into war. Sure, Serbia played a role, but so did the EU with its harmful Badinter Commission.
Reports from Africa aren't very encouraging either. Finding a solution for the insurrection of the LRA in Uganda is seriously hampered by an ICC indictment of its leader Kony - that makes it impossible to offer Kony impunity in exchange for an end to the violence. More recently we see similar developments in Eastern Congo around the indictment of Ntaganda that led to the formation of the M23. Another tool of our modern "humanitarian warriors", the boycott of "blood diamonds" and other minerals led to their recent offensive.
And then there is Bangladesh. As the Economist recently reported (The trial of the birth of a nation) it has its own tribunal for crimes during its independence war in 1971. Yet the tribunal was only set up in 2008 and it seems mainly meant to harass the Islamist Jamaat party that during that war was allied with the Pakistani and is now part of the opposition.
Jadaliyya, an Arab magazine, has an article "Imagining Justice Beyond the ICC". It tells in detail how both the ICC and the R2P principle are in practice dependent on the main world powers for the supply of suspects and witnesses and how that undermines its neutrality.