Good: impunity is a bad thing. Those who break those norms of international law , and commit war crimes, crimes against humanity and the crime of aggression should be prosecuted - on all sides. Actions by Hamas and other organizations that are reprehensible are matters that should be brought before impartial courts, too.  While there is no international international definition of terrorism, there are a number of acts which are prohibited by particular treaties – they can be prosecuted too.