The Null Device
It's official: according the the UN, American nationals cannot, by definition, be war criminals, and crimes against humanity can only be committed by non-US nationals. At least for the next 12 months, renewable annually. And so, justice comes from the barrel of the biggest gun.
(What happens when China comes into its own as a world superpower, and demands that Chinese nationals be exempted from prosecution, threatening to sabotage the UN process if it's unfairly denied this privilege that the US has (as would be the rational thing for China to do faced with such a snub); or when Israel pushes for exemption for its operations in the Palestinian territories, with US backing? Or when Indonesia (the world's third most populous nation, and a potential economic and military powerhouse) starts doing so, and pushing its weight around? Or when a dozen other countries do the same? The criterion for exemption from prosecution doesn't seem to be anything other than "might makes right" (unless you believe in the doctrine of America's God-given Manifest Destiny or some other system of teleological mumbo-jumbo, of course). So we'll end up with a club of powerful nations who are above the law, and a puppet kangaroo court existing solely to try their defeated enemies and keep the small fry from rising above their station in world affairs.)