A secret memo outlining the U.S. government's justification for the use of drones to kill American terrorism suspects abroad was released by court order on June 23.
The heavily redacted memo said the authority to use lethal force abroad may apply in certain circumstances to a U.S. citizen who is part of the forces of an enemy organization.
The July 2010 memo was released after a year-long legal battle by "The New York Times" and the American Civil Liberties Union.
The memo specifically provided the legal justification for the September 2011 killing in Yemen of Anwar Al-Awlaki, a U.S.-born Muslim cleric born with connections to several terrorism suspects, and another U.S. citizen, Samir Khan, who edited Al-Qaeda's Internet magazine.
An October 2011 strike also killed al-Awlaki's teenage son, also a U.S. citizen.
The memo said Al-Awlaki had been involved in an abortive attack against the United States and was planning other attacks.
Based on reporting by AP and dpa