An 11-page section at the front of the memo was redacted. It compiled the evidence to support the intelligence community’s assertion that Mr. Awlaki was not merely a propagandist but an operational terrorist.

Image Anwar al-Awlaki in 2010. Credit... Agence France-Presse — Getty Images

But on Monday the appeals court issued a new public version of a ruling it made in April that the memo must be made public, and it included passages that had been redacted. Among those passages were instructions from the court to make related Office of Legal Counsel memos available to a Federal District Court judge for review and possible release.

The Justice Department’s memo from July 2010 makes reference to an earlier memo, also written by Mr. Barron, that focused largely on constitutional issues in targeting Mr. Awlaki. The Times has reported that after the attempted bombing of a Detroit-bound airliner on Dec. 25, 2009, to which Mr. Awlaki was linked, Mr. Barron and Mr. Lederman swiftly wrote a short memo approving the targeting of Mr. Awlaki if he was located.

Later, after seeing a post on an international law blog that raised the statute banning the murder of Americans abroad, which their first memo did not address, they went back and wrote the lengthier July 2010 memo.

The longer memo argues that the killing of a wartime enemy by the military would qualify for a “public authority” exception to the foreign murder statute. A section about the possibility that the C.I.A., a civilian agency, might carry out the killing appears to invoke similar reasoning but is heavily redacted; one portion also argues that it would not be a war crime for the agency to carry out the killing.

Jameel Jaffer, a lawyer for the A.C.L.U., called the release of the memo “an overdue but nonetheless crucial step toward transparency.” He added: “There are few questions more important than the question of when the government has the authority to kill its own citizens. This memo’s release will allow the public to better understand the scope and implications of the authority the government is claiming.”

In October 2011, a week after the strike, The Times reported on the contents and bureaucratic history of the memo, classified at the time, and filed an information act request for it. The newspaper and the A.C.L.U. filed separate lawsuits seeking its public disclosure several months later.