(4) of a person who, in relation to an armed conflict and
      contrary to the provisions of the Protocol on Prohibitions or
      Restrictions on the Use of Mines, Booby-Traps and Other Devices
      as amended at Geneva on 3 May 1996 (Protocol II as amended on 3
      May 1996), when the United States is a party to such Protocol,
      willfully kills or causes serious injury to civilians.