This book began with a quotation from the federal judge hearing the civil suit brought by the family of Anwar al-Awlaki in order to emphasize the fact that the variety of civilians involved in these shadowy conflicts even includes the judiciary, and to underscore the salience of legal issues to debates about how the United States should conduct operations in today's gray area of war. Those killings awakened the American public to the problems of UAV use and caused widespread international concern – even alarm – and an unusual amount of comment. Questions about drone attacks reached the federal courts before the executive branch officially acknowledged their existence. The leaked February 2013 Department of Justice White Paper that developed legal justification for targeted killings of Americans was a complex, intricately detailed memorandum that addressed both U.S. domestic law and international law. But it raised as many questions as it answered. An even more detailed classified legal memorandum was supplied to select members of Congress, and a redacted version made public in mid-2014, when it first seemed that its author, David Barron, would not receive the necessary votes for confirmation as a U.S. appellate judge. Although officials have outlined the legal rationale for such actions to specialized audiences, it took a U.S. Court of Appeals decision to compel the government to reveal a more detailed legal basis for targeted killings by UAVs. The question of whether and when such operations are lawful – especially the targeting of U.S. citizens under American constitutional law – has only been grudgingly and partly addressed. The U.S. government has not fully and persuasively presented either the international nor the domestic legal basis for such operations.

Legal issues surrounding targeted killing differ from those of counterinsurgency, whose operations pose no major issues about legality, except perhaps in terms of the rationale for intervention in the first place. By contrast, targeted killing raises troubling questions of legality. These issues may only affect the definition of civil-military roles tangentially. But doubts about both U.S. domestic and international legality create problems for international allies, for American national leadership, for the public whose support is necessary, and for the men and women in the chain of command who both mandate and perform operations.