The U.S. Court of Appeals for the Second Circuit has released a secret Justice Department memo explaining why killing U.S. citizen Anwar al-Awlaki was justified.



The court released the document as part of a Freedom of Information Act lawsuit filed by The New York Times and the American Civil Liberties Union to make the document public, The Hill reported Monday.



Al-Awlaki was killed in a drone strike in 2011.



The memo is 41 pages long and partly redacted, but in it, then-acting Assistant Attorney General David Barron explains why the drone strike in Yemen was needed. Al-Awlaki, he explained, was an alleged operational leader of al-Qaida.



"The U.S. citizen in question has gone overseas and become part of the forces of an enemy with which the United States is engaged in an armed conflict; that person is engaged in continual planning and direction of attacks upon U.S. persons from one of the enemy's overseas bases of operation; the U.S. government does not know precisely when such attack will occur; and a capture operation would be infeasible," Barron wrote, according to the report.



The Hill says Attorney General Eric Holder explained last year about when the U.S. is within its powers to target one of it's own.



"The suspect must pose an imminent threat, capture must be infeasible, and the strike needs to adhere to applicable war principles," Holder said.



Democratic Sens. Mark Udall and Ron Wyden say that while they applaud the release of the document, the Obama administration still has some explaining to do, the report says.



"How much evidence does the president need to determine that a particular American is a legitimate target for military action?" Wyden asked, according to The Hill. "Or, can the president strike an American anywhere in the world? What does it mean to say that capturing an American must be 'infeasible'? And exactly what other limits and boundaries apply to this authority?"



New Mexico-born al-Awlaki was said to have helped in the planning of the Fort Hood massacre and the "underwear bomber" plot, the site reports.



In the memo, Barron says the Authorization of Use of Military Force (AUMF) approved by Congress in 2001 could be used to justify the strike.



"Al-Awlaki, an active, high-level leader of an enemy force who is continually involved in planning and recruiting for terrorist attacks, can on that basis fairly be said to be taking 'an active part in hostilities,' " the memo reads, according to the report.



Jameel Jaffer, the ACLU's deputy legal director, told Time that the memo is important for what it reveals about the drone program.



"There are few questions more important than the question of when the government has the authority to kill its own citizens," he said, according to the magazine.



"This memo's release will allow the public to better understand the scope and implications of the authority the government is claiming. We will continue to press for the release of other documents relating to the targeted killing program, including other legal memos and documents relating to civilian casualties."



