A US federal appeal court ordered the Department of Justice to turn over key portions of a memorandum justifying the government's targeted killing of people linked to terrorism, including Americans.
In a case pitting executive power against the public's right to know, the court of appeals reversed a lower court ruling preserving the secrecy of the legal rationale for the killings, such as that of US citizen Anwar al-Awlaki in a 2011 drone strike in Yemen.
A three-judge panel ruled unanimously in favour The New York Times, saying the government waived its right to secrecy by making repeated public statements justifying targeted killings.
These included a Justice Department "white paper", as well as speeches or statements by officials such as Attorney General Eric Holder and former Obama administration counterterrorism adviser John Brennan, endorsing the practice.
The Times and two reporters, Charlie Savage and Scott Shane, sought the memorandum under the federal Freedom of Information Act (FOIA), saying it authorised the targeting of Awlaki, a cleric who joined al-Qaeda's Yemen affiliate.
"Whatever protection the legal analysis might once have had has been lost by virtue of public statements of public officials at the highest levels and official disclosure of the DOJ white paper," Circuit Judge Jon Newman wrote for the appeals court panel in New York.
He said it was no longer plausible to argue that disclosing the legal analysis could jeopardise US military plans, intelligence activities or foreign relations.
The court redacted a portion of the memorandum on intelligence gathering, as well as part of its own decision. It is unclear when the memorandum or the full court decision might be made public, or whether the government will appeal.
Allison Price, a Justice Department spokeswoman, said the department had no comment on the decision.
David McCraw, a lawyer for the Times, said the newspaper was delighted with the decision.
"The court reaffirmed a bedrock principle of democracy: the people do not have to accept blindly the government's assurances that it is operating within the bounds of the law."
Senators Patrick Leahy and Charles Grassley, the Democratic chairman and senior Republican on the Senate Judiciary Committee, have also been seeking the legal rationale, and Grassley on Monday urged the Justice Department to start preparing to turn it over.
Monday's decision largely reversed a January 2013 ruling by US District Judge Colleen McMahon. She ruled for the administration despite scepticism over its antiterrorism programme, including whether it could authorise killings outside of a battlefield.
"The Alice-in-Wonderland nature of this pronouncement is not lost on me," she wrote.
Civil liberties groups have argued that the drone programme lets the government kill Americans without constitutionally required due process.
FOIA requests at issue in the court of appeals case also focused on drone strikes that killed two other US citizens: Awlaki's teenage son, Abdulrahman al-Awlaki, and Samir Khan, who was an editor of Inspire, an English-language al-Qaeda magazine.
McMahon ruled one month before the Justice Department released the white paper, which set out conditions before lethal force could be used against US citizens in foreign countries.
The conditions are that a top US official must decide a target "poses an imminent threat of violent attack" against the United States, the target cannot be captured, and any operation would be "consistent with applicable law-of-war principles".