Marty Lederman and David Barron wrote the authorization to kill Anwar al-Awlaki.
Martin "Marty" S. Lederman He has concentrated on questions involving freedom of speech, the Religion Clauses, congressional power and federalism, equal protection, separation of powers, copyright, and food and drug law. He helped draft the June 2010 memorandum authorizing the targeted killing of U.S. citizen and Islamic cleric Anwar al-Awlaki. 
Lederman is currently on leave from his position as Associate Professor of Law at the Georgetown University Law Center. He teaches courses in constitutional law, separation of powers, and executive branch lawyering. When not serving in government, he has been a regular contributor to the weblogs SCOTUSblog and Balkinization. His blogging and scholarship focuses on matters related to executive power, detention, interrogation, civil liberties, and torture.
Lederman was formerly an attorney at Bredhoff & Kaiser, where his practice consisted principally of federal litigation, including appeals on behalf of labor unions, employees and pension funds, with particular emphasis on constitutional law, labor law, civil rights, Racketeer Influenced and Corrupt Organizations Act (RICO) and employment law. He graduated from University of Michigan and Yale Law School.
- Harvard College A.B. 1989, History
- Harvard Law School J.D. 1994
- Chair, Section on Local Government Law, AALS
- Assistant Professor of Law, 1999
- Professor of Law, 2004
- Honorable S. William Green Professor of Public Law, 2011http://www.law.harvard.edu/faculty/directory/index.html?id=4
=====Robert M. Chesney, a University of Texas School of Law professor who specializes in national security law, said he believed the killing was legal. But he said it was "plenty controversial" among legal experts.
The administration's legal argument in Awlaki's case, Chesney said, appears to have three elements: First, Awlaki posed an imminent threat to the lives of Americans; second, he was fighting with the enemy in the armed conflict; and third, there was no feasible way to arrest him.
"Under these circumstances, I don’t have grave due process anxieties about targeting a U.S. national."
"Let’s hold up what we know about the Al Aulaqi case to this test:
(1) He has clearly been identified with a high degree of confidence using the best intelligence available and a multi-layered review process as a high-level operational terrorist leader in a group that the government reasonably regards as part of Al Qaeda (or at least cobelligerent with it) and who has actually planned attacks on behalf of that group. Critically, this intelligence, some of which has become public, is notsimply about his role as a charismatic, inspirational jihadist cheerleader or as an internet propagandist, facts that would not, repugnant though these activities are, be grounds for targeting him.
(2) Efforts to capture Al Aulaqi have clearly been made. This morning’s New York Times, for example, has a lengthy story about such efforts over a long period of time:
But in fact, the Yemeni security services, many trained by American Special Forces soldiers, appear to have pursued Mr. Awlaki for almost two years in a hunt that was often hindered by the shifting allegiances of Yemen’s tribes and the deep unpopularity of Mr. Saleh’s government.In 2009 and 2010, Mr. Awlaki seems to have been mostly in the southern heartland of his own powerful tribe, the Awaliq, where killing him would have been politically costly for the government, and capturing him nearly impossible. The area where Mr. Awlaki was finally killed, in the remote north, did not afford him the same tribal protection. There are also many tribal leaders in the far north who receive stipends from Saudi Arabia — the terrorist group’s chief target — and who would therefore have had more motive to assist in killing him.The hunt for Mr. Awlaki has involved some close calls, including the failed American drone strike in May, and the previously unreported operation in the Yemeni village. Yemen’s elite counterterrorism commandos, backed by weapons from Yemen’s regular armed forces, formed a ring around the town as commanders began negotiating with local leaders to hand Mr. Awlaki over, said one member of the unit.“We stayed a whole week, but the villagers were supporting him,” said the counterterrorism officer, who is not authorized to speak on the record. “The local people began firing on us, and we fired back, and while it was happening, they helped him to escape.”
What’s more, Al Aulaqi has been on notice for quite some time that he is wanted and has not sought to surrender or turn himself in, and the government has made clear it would accept his surrender. So there’s a strong basis on which the government can argue here that it has pursued remedies short of lethal force. It has tried to take Al Aulaqi alive and remained open to the possibility but the chance did not pan out. What did pan out was an opportunity to attack a car from a remote, stand-off position.
(3) Would the foreseeable result of not taking this chance have been the loss of innocent life? This question seems to me to answer itself. A government worth anything simply has to take seriously a man who has been personally involved in terrorist actions in the past, who promises more, and who is taking active steps to conduct them."