There is a system of international law with rules, enforcement and punishment. The ICC, based in the Hague, with Milosevic in the dock.
However, the US doesn't recognise the jurisdiction of the ICC over its troops and the ICC has no power over "crimes of aggression" and investigates "lesser" crimes such as genocide!
Therefore the only ones to end up in the dock are enemies of the US and British armed forces personnel hung out to dry by the MoD. There's about as much chance of Bliar appearing in the dock as there is of his missus buying a Big Issue.