A man inspects a site targeted by what activists said was a poison gas attack in the village of Sarmin in Idlib province March 17, 2015. REUTERS/Mohamad Bayoush

(Reuters) - Memorandums on the legal basis for targeted killings of people in other countries that the U.S. government believes are involved in militant attacks can be kept secret, a federal court ruled in a document released on Monday.

A three-judge panel of the New York-based U.S. 2nd Circuit Court of Appeals denied an effort to obtain the memos by the New York Times and the American Civil Liberties Union (ACLU) under the U.S. Freedom of Information Act.

The ruling was detailed in a 22-page opinion reached last month but placed under temporary seal.

The legal action by the New York Times and the ACLU seeking the release of the documents was launched after a 2011 drone strike in Yemen that killed U.S. citizen Anwar al-Awlaki, a cleric who joined al Qaeda’s affiliate in that country and directed several attacks.

The same appeals court decided last year to release key portions of a 41-page memorandum from 2010 on drone killings, on the grounds that senior U.S. government officials waived the right to secrecy for that particular document by making repeated public statements justifying targeted killings.

The ACLU and the New York Times had then sought the release of certain other memos from the U.S. Department of Justice’s office of legal counsel on targeted killings but a district court ordered them withheld.

ACLU attorneys and lawyers for the New York Times argued in their latest appeal that the memos constituted “working law” that must be publicly released.

In his opinion, however, Judge Jon Newman denied that argument to force the disclosure of the memos from the office of legal counsel.

“At most, they provide, in their specific contexts, legal advice as to what a department or agency ‘is permitted to do’ ... and its advice ‘is not the law of an agency unless the agency adopts it’,” Newman wrote, in quoting from a related federal court decision from 2014.