Shortly after September 11, 2001, President George W. Bush, as Commander in Chief, authorized unmanned aerial vehicles (UAVs), or drones, to target and kill enemy leaders pursuant to Congress’ Authorization for Use of Military Force (AUMF) against al Qaeda. The President designated “Afghanistan and the airspace above” a combat zone, but the United States also launched drone strikes against al Qaeda targets in other countries. The drone program received widespread attention in November 2002, when the C.I.A. launched a Predator drone strike in Yemen, killing the mastermind of the October 2000 attack on the U.S.S. Cole and six other men. Following the Yemen attack, the United Nations Special Rapporteur on Extrajudicial, Summary, or Arbitrary Executions asserted that the attack in was “a clear case of extrajudicial killing.” In response, the U.S. defended the drone strike as permissible under international law of armed conflict, broadly asserting that al Qaeda terrorists who continue to plot attacks may, in appropriate circumstances, be lawful subjects of armed attack without regard to their location...