They're judged in American military courts. The US military has a strict set of laws called the Uniform Code of Military Justice, or UCMJ. The soldiers responsible for the inhumane treatment at Abu Ghraib,for example, were all sentenced. The soldier who killed locals for fun in Iraq was prosecuted and given a long sentence.

Soldiers guilty of violating these laws are given sentences at military prisons in the United States. They're forced to do hard labor, they follow a strict daily regimen that most would consider hell. Fort Leavenworth is one such prison.

I get the hint that many Dutch feel like this is so Americans can get away with war crimes when it's more about keeping sensitive information secret. An international court is probably not the best place to expect sensitive information, like troop movements or military tech, to remain secret.