I don't see what you are all worrying about. Surely your American Congress will put down some nice magical legislation trick that makes it legal for the US to invade one of its allies to 'liberate' American citizens held captive by a war tribunal? That's how they settled a possible problem with the International Tribunal in The Hague, didn't they?

Would be kinda interesting to see American GI's invading the tourist beaches of Scheveningen or the Costa del Sol and taking the local prison by force though...