Um, well, the one-sideness of how everything is treated? An European boy charged with making a website aggravating an American corporation? Handcuff and to the plane (yep, that was stopped by a court, but still)! An American businessman charged with commanding the murder of an European chief of police? No, sorry, we won't hand you our citizen (search for the case of general Papała).

Even if this is not stated in any treaties, it's simply the practice.