Aren't all courts politically driven?
We have international police nicely co-operating, so why not international courts? You want the police to catch the bad guys, and then have no foot to stand on because there's no laws? I'm pretty sure any cop will tell you that the worst thing about the job is the justice apparatus not being up to par.

It's an attempt for change. If an Iranian soldier would murder an American soldier in Congo, would you still be against an international court? Would you still take the risk of an Iranian court letting the Iranian soldier go? Congo wouldn't care - what if Iran wouldn't care (and they don't)? An international court is an attempt to change those rules. The Iranians could say "No! We only want Iranians to be tried in Iranian courts!" - yeah, good luck... they'd probably get a medal. I can understand Iran to be against an international court, but the US?

And Belgium has a very healthy economy: the debt is around 100% of the GDP (in the US, it's only 62%), and a perfect budget (let's not talk about the US budget, shall we)... I know you snuck that comment in especially for me