Anwar al-Awlaki, a U.S.-born cleric linked to al Qaeda's Yemen-based wing, gives a religious lecture in an unknown location in this still image taken from video released by on Sept. 30, 2011. Reuters

The Department of Justice asserted it is lawful to approve the targeted killing of a United States citizen if that person is a ranking figure in al-Qaeda, or a comparable terrorist group, who poses an “imminent threat of violent attack” against the United States, and his immediate capture is not possible, according to a white paper released Monday night.

The 16-page memo, first obtained by NBC News, offers the first look at the criteria the Obama administration has used to justify the killing of American citizens abroad, without the benefit of due process. Although the administration has reportedly ordered hundreds of drone strikes against foreign-born targets suspected of participating in anti-American terrorist activity – primarily in Pakistan and Yemen – the president was met with pronounced criticism from civil liberties groups after ordering the killing of American-born cleric Anwar-al-Awlaki.

Al-Awlaki, who was reportedly a senior leader in al-Qaeda, was born in New Mexico and killed by a missile fired from a drone in September 2011 in Yemen. His 16-year-old son Abdulrahman al-Awlaki, also an American citizen, was killed two weeks later in another American drone strike.

In 2010, Al-Awlaki’s father attempted to sue the United States government after his son was placed on the CIA’s targeted kill list. However, the case was dismissed from courts after the White House invoked the state secrets privilege.

In its legal analysis, the Justice Department argues that, under the laws of war, the United States can use lethal force against a U.S. citizen overseas if he or she is “an operational leader continually planning attacks against U.S. persons and interests, in at least the following circumstances: (1) where an informed, high level official of the U.S. government has determined that the targeted individual poses an imminent threat of violent attack against the United States; (2) where a capture operation would be infeasible – and where those conducting the operation continue to monitor whether capture becomes feasible; and (3) where such an operation would be conducted consistent with applicable law of war principles. In these circumstances, the ‘realities’ of the conflict and the weight of the government’s interest in protecting its citizens from an imminent attack are such that the Constitution would not require the government to provide further process to such a U.S. citizen before using lethal force.”

In its definition of “imminent threat,” the department said it is not necessary for a specific attack to be in progess when a target is located if that target has generally been engaged in terrorist activities against the United States.

Anwar Al-Awlaki was linked to multiple terrorist attacks, including the 2009 Fort Hood shootings and the attempted attack by Faisal Shahzad, the man who tried to set off a car bomb in Times Square in 2010.

The release of the white paper comes days before the Obama administration’s nominee for CIA chief, John Brennan, is scheduled to testify before the Senate Intelligence Committee.

The memo, while providing a detailed look into the criteria the administration uses to justify the killing of an American overseas, does not carry legal weight.

On Tuesday, eight Democratic and three Republican senators – including some members of the Intelligence Committee – sent a letter to the president asking him to provide the legal opinions outlining his power to authorize the killing of American citizens during the course of counterterrorism operations.

“It is vitally important, however, for Congress and the American public to have a full understanding of how the executive branch interprets the limits and boundaries of this authority, so that Congress and the public can decide whether this authority has been properly defined, and whether the President’s power to deliberately kill American citizens is subject to appropriate limitations and safeguards,” the senators wrote.