In a rare public ruling by the nation’s most secretive judicial body, the Foreign Intelligence Surveillance Court ruled Wednesday that it did not object to the release of a classified 86-page opinion concluding that some of the U.S. government’s surveillance activities were unconstitutional.

The ruling, signed by the court’s chief judge, Reggie Walton, rejected the Justice Department’s arguments that the secret national security court’s rules prevented disclosure of the opinion. Instead, the court found that because the document was in the possession of the Justice Department, it was subject to release under the Freedom of Information Act.

Privacy advocates who brought the case said Wednesday that the ruling could pave the way for at least the partial release of landmark -- but still classified -- court rulings that some government surveillance activities violated the Fourth Amendment of the Constitution barring "unreasonable searches and seizures."

The release of the opinion, they say, may prove central in the current controversy over the scope of National Security Agency surveillance programs.

“It’s a brand new day,” said Kurt Opsahl, a senior staff attorney with the Electronic Frontier Foundation, a privacy group that brought the case. He noted that it is extremely rare for any FISC ruling to be made public at all, much less for the court to rule on behalf of disclosure advocates over the objection of Justice Department lawyers.

A spokesman said the Justice Department was reviewing the ruling and declined further comment.

The EFF’s lawsuit was inspired by a July 20, 2012 letter from an aide to Director of National Intelligence James Clapper to Sen. Ron Wyden, D-Ore., that stated that “on at least one occasion,” the FISC held that “some collection” carried out by the U.S. government under classified surveillance programs “was unreasonable under the Fourth Amendment.”

The letter, from Kathleen Turner, Clapper’s chief of legislative affairs, provided no further information about what the FISC found to be unconstitutional, but did state that the government “has remedied these concerns” and the FISC has continued to approve its collection activities.

Wyden, a member of the Senate Intelligence Committee, has said he was barred from speaking any further about the matter because it remained classified.

The EFF last year filed a lawsuit to compel disclosure of the FISC opinion under the Freedom of Information Act. As part of the case, the Justice Department acknowledged there was in fact an 86-page opinion by the FISC dated Oct. 3, 2011, that was responsive to the FOIA request. But department lawyers argued that the FISC opinion could not be released because the court’s own rules barred public disclosure.

In Wednesday’s seven-page opinion, Judge Walton found otherwise, siding in part with the EFF over the Justice Department. He concluded that a FISC rule requiring that its opinions be sealed did not apply to an opinion in the government’s possession that had not otherwise been barred from disclosure.

The ruling did not order the immediate release of the opinion, however, instead referred the matter to a lower court for a final decision on whether the opinion is eligible for release under FOIA, which requires the government to release documents not covered by security or other narrow exemptions.

However, Walton did not immediately order the DOJ to release the order. Instead, he wrote, “This court expresses no opinion on the other issues presented” in the FOIA case “including whether the opinion is ultimately subject to disclosure.”

Such questions, he wrote, are "appropriately addressed” by the federal court in which the EFF lawsuit was originally filed.

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