The possibility that members of this administration will be brought up on charges in a foreign country seems extremely remote.  This is how war crimes prosecutions work: the only people ever prosecuted for war crimes are either the leaders of governments defeated in war or the former leaders of extremely weak and vilified nation-states that think they can get back some international respect by throwing the old ruler to the wolves.  Occasionally, you get a gratuitous case of a foreign judge engaging in moral self-importance, as you had with the whole sorry Pinochet episode.  If you are on the “right” (i.e., winning) side of a conflict, as far as international tribunals are concerned your government officials have not meaningfully authorised war crimes, no matter what your government has or has not done.  As vilified as our government may be in some parts of the globe, no elected European or any other allied government is going to provoke an international incident by allowing or ordering the arrest of Donald Rumsfeld (or any of the others), the other major powers wouldn’t want the headache, no one else cares enough to bother, and so the threat that any of them will be arrested and tried is entirely toothless.  

Megan McArdle is right about this–the public reaction to such an arrest, much less a trial, would be intensely hostile.  I would go so far as to say that it would create such hostility to the nation whose government carried out the arrest that citizens of that country would probably be advised not to visit the U.S.  Obviously, no future U.S. administration is going to sit idly by and allow such a trial to take place, not least since it would create all kinds of precedents that would make the sitting President and his officials vulnerable to prosecution for any decisions they may make.  You would see bizarrely popular boycotts of imports from said country that make the French wine boycotts of ’02-’03 seem like a friendly, low-key affair, and there would be random “Free Rumsfeld” (or whoever) banners strewn all over the place.  No doubt there would be some country-rock song commemorating popular outrage. 

This is the absurd double-standard that hegemonism requires that we impose: our government may do what it wants when it wants, and your government will do what is demanded of it or else; our officials are entirely unaccountable, while yours may be put on trial and may even be put to death if we are so inclined.  Even better than worrying about whether administration officials would be arrested and tried for their crimes overseas is to hold them accountable within our constitutional system, but that is even more far-fetched and unrealistic.