Is every justice system in the world subservient to the American system?
It seems more reasonable to return him to where he committed the crime (Kosovo?) and have him dealt with there, doesn't it?
Kosovo is a dysfunctional pseudo-state that exists in limbo between two states that don't really want that mess to be integrated into their polities: Serbia and Albania. Serbia is Orthodox Christian and Albania is an extremely moderate predominantly Muslim country. Neither of them are comfortable with ISIS supporters in their backyards. Malaysia sure as heck doesn't want ISIS supporters either. So what you call subservience is rather simply all of the parties involved except Kosovo effectively saying "this guy targeted the US Government, the US Government wants him and we sure as hell don't want him. Let the US Government spend the time and resources to clean this guy's clock."