The recent events in Paris highlight the fact there is no such thing as international law.  Countries do have treaties with one another and they or may not be honored.  The United Nations passes resolutions but has no power to enforce them.  There is a World Court but it only works if all the parties agree to be bound by the decision in advance, and then actually abide by it.

     The acts committed in Paris are not crimes as such because the ones that committed them do not recognize the law.  They could be prosecuted if caught but that is highly unlikely.  There is no international organization that has the power or authority to hunt down terrorists and arrest them.  With all of the weaknesses in our legal system it is still a shining star when compared to the virtually nonexistent international order.