The Obama administration’s justification for the killing of American citizen Anwar al-Awlaki in 2011 has always been somewhat murky.

Awlaki was killed in Yemen along with another American, Samir Khan (editor of the al Qaeda magazine “Inspire”), when a missile fired from an American drone struck the car in which they were riding.

The best explanation of the legality of the killings was in a Justice Department “white paper” leaked by NBC in February 2013. It stated a cogent - if troubling - rationale. It said that if: (1) an “informed high level official of the US government” decided that the person posed an imminent threat of violent attack against the United States; and (2) capture was infeasible; and (3) the operation would be conducted in accordance with the law of war, then an American citizen who was a senior leader of al Qaeda or an associated force outside the United States could be assassinated by our government.

Many people were troubled by the power found to exist in any “informed high level official” to order the death of an American without due process of law. I was not one of them. A person who forswears his allegiance to America in favor of al Qaeda has become an enemy combatant who can be lawfully killed in battle by any American soldier. That is the law of war. In that respect, killing Awlaki with a drone strike was no different from the carefully-planned shooting down of Japanese Adm. Isoroku Yamamoto’s aircraft in 1943.

On Monday, the court-ordered release of a 31-page redacted Justice Department legal opinion revealed more of the rationale behind the Obama administration's claim to the authority to kill American citizens without due process of law.

It begins by making clear that an American who kills another American outside the jurisdiction of the United States is guilty of murder. Going further than the Justice Department white paper, it invokes the “public authority” justification for law-breaking that covers acts such as a fire engine running a stop light to reach a fire. It concedes that the “public authority” justification doesn't cover all actions by the Executive Branch, but finds - as the white paper did - that the September 2001 Authorization for Use of Military Force authorized the president to kill an American who was associated with al Qaeda-related forces such as Awlaki.

But the legal opinion doesn't - and can't - explain why Anwar al-Awlaki, an American citizen, was killed by a drone strike while Ahmed Abu Khattala, a Libyan suspected of leading the 2012 attacks on our missions in Benghazi, taken alive?

It isn't that Abu Khattala was more valuable. Awlaki, a top leader of al Qaeda in the Arabian Peninsula, was alleged to have knowledge of planned attacks and thus had much more intelligence information that could have been extracted were he taken alive.

The difference between Awlaki’s assassination and Abu Khattala’s capture is purely political. Neither the Yemenis nor the Libyans would have given us permission cross their borders to capture those men. That doesn’t mean that capture was infeasible. The Libyans barely have a government, so their permission is irrelevant.

There were political benefits to Obama and the Yemenis in killing Awlaki. It extended Obama's power into uncharted territory and it was easier for the Yemenis to explain to their sometime terrorist allies than if they allowed us to capture him. Fox, CNN and CBS were all able to track down Abu Khattala for interviews in the weeks after the Benghazi attacks so our military must have been able to find him at least as easily. But killing Abu Khattala would have deprived Obama of another show trial in federal court to support his goal of closing Guantanamo Bay's terrorist prison.

The most troubling issue that remains is who exercises the power of the “informed high level official of the US government,” and can he be trusted with these life or death decisions? The person who makes those decisions is Obama. His decisions are about politics, not about winning the war.

Jed Babbin served as a deputy undersecretary of defense in the George H.W. Bush administration and is a senior fellow of the London Center for Policy Research. He is the author of "The BDS War Against Israel," with Herbert London.