The International Criminal Court isn't perfect as it has no authority to send out its own police force to arrest someone. However, when someone is turned over to authorities on behalf of the ICC, the criminal court seems to do its job when it brings in someone accused of war crimes. The difficulty is that by the time the ICC files charges, it is usually too late for the death and destruction certain people have caused.
The trials at Nuremberg where the subject of huge moral debate that continues to this day. The ICC was created afterword in order to prevent some of the mistakes made at Nuremberg and build on the good that was also done there. While the process is not finished the ICC is a huge step forward to preventing the atrocities we have previously faced.