The colonials might feel odd about someone from out of their civilization to make them obey their laws.
We turned IMG for a reason (and are a different civilization with good enough laws)
Nice idea anyway - imo it should be a Liberty-based court - much like the court in Strasbourg - human rights, war crimes etc... Not many recognize it, (because frankly the court shouldn't be recognized) but still the world powers like the US and Europe make puny lil' dictators like Saddam or Milosevic stand before it.