A secret U.S. Justice Department memo obtained by NBC News shows American citizens can be assassinated if they are deemed to be senior leaders associated with Al Qaeda , or an offshoot of the militant network.
The memo offers more detail of the legal thinking behind the use of drones to kill Al Qaeda operatives, such as Anwar al-Awlaki  and Samir Khan , who were both killed in strikes without a normal legal indictment or charges brought against them.
The document  broadens the definition of who can be targeted and when, saying there does not need to be “clear evidence” that the target is planning to attack the U.S. in the near future.
Instead, a high-level official can order the strike, based on his or her own assessment of the intelligence. If capturing a suspect is viewed as posing an “undue risk” to U.S. officials, targeted killing can be given the green light.
Attorney General Eric Holder endorsed the drone assassination program  in March, 2012, and it has become a central issue in the hearing of the campaign’s key architect and possible Central Intelligence Agency chief, John Brennan.
The U.S. CIA drone campaign began in 2002, but since President Barack Obama came to office in 2008 there has been a marked upsurge in the use of drones in Yemen , Pakistan and Somalia.
“This is a chilling document,” Jameel Jaffer, deputy legal director of the ACLU, which is suing to obtain administration memos about the targeted killing of Americans, told NBC. “Basically, it argues that the government has the right to carry out the extrajudicial killing of an American citizen. … It recognizes some limits on the authority it sets out, but the limits are elastic and vaguely defined, and it’s easy to see how they could be manipulated.”