Additional details about the strike on al Qaeda’s Anwar al-Awlaki in Yemen became available yesterday after news of his demise, including the realization that it was not Yemeni forces responsible for the attack, but rather, a U.S. drone strike. The mission was carried about between the CIA and JSOC.

Because Awlaki was an American — as was another al Qaeda member, Samir Khan, who was also killed in the same strike — questions remain about the legality of the attack. The Washington Post reports on the internal administration legal document justifying the action.

The Justice Department wrote a secret memorandum authorizing the lethal targeting of Anwar al-Aulaqi, the American-born radical cleric who was killed by a U.S. drone strike Friday, according to administration officials.

The document was produced following a review of the legal issues raised by striking a U.S. citizen and involved senior lawyers from across the administration. There was no dissent about the legality of killing Aulaqi, the officials said.

“What constitutes due process in this case is a due process in war,” said one of the officials, who spoke on the condition of anonymity to discuss closely held deliberations within the administration.

The administration has faced a legal challenge and public criticism for targeting Aulaqi, who was born in New Mexico, because of constitutional protections afforded U.S. citizens. The memorandum may represent an attempt to resolve, at least internally, a legal debate over whether a president can order the killing of U.S. citizens overseas as a counterterrorism measure.

In a statement, and Obama administration official argued, “As a general matter, it would be entirely lawful for the United States to target high-level leaders of enemy forces, regardless of their nationality, who are plotting to kill Americans both under the authority provided by Congress in its use of military force in the armed conflict with al-Qaeda, the Taliban, and associated forces as well as established international law that recognizes our right of self-defense.”

As for Awlaki’s role in the terrorist network — and whether his role was limited to propaganda, or whether he was a more active leader, involved in directing terrorist plots — officials also identified Awlaki yesterday as the “external operations” chief for al Qaeda in the Arabian Peninsula. The label matters, to the extent that it seeks to provide additional justification — U.S. forces weren’t just targeting some guy who made radical videos, the argument goes, forces were also targeting a guy actively involved in directing terrorist attacks against civilians.

For more on this and the larger debate, I found this discussion between Rachel Maddow and Spencer Ackerman very worthwhile.

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Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.