(CN) - Disclosing a ruling showing how the government proposed using data that the National Security Agency tapped from the "Internet's backbone" could "reasonably be expected to cause grave damage to national security," a federal judge ruled.
The Electronic Frontier Foundation, a digital civil liberties group that filed the lawsuit last year, did not respond to a request for comment by press time.
The group's Freedom of Information Act case centers on rulings by the Foreign Intelligence Surveillance Court, which operates out of an undisclosed room in Washington federal courthouse.
Although EFF originally filed four separate requests, the group withdrew many of its requests after the Department of Justice disclosed various documents.
It kept on pursuing the production of a FISC opinion relating how the government proposed using data that the NSA acquired via "Upstream" collection, a term for pulling telephone and Internet traffic from domestic and foreign cables and switches.
The group learned about the existence of this opinion after it was cited in an Oct. 3, 2011, FISC opinion that it obtained through a different lawsuit.
The Justice Department fought off the request with a declaration from the NSA's assistant director David Sherman, who testified that the document was properly classified as "top secret."
"Specifically, the release of the redacted information would disclose sensitive operational details associated with NSA's 'Upstream' collection capability," Sherman said. "While certain information regarding NSA's 'Upstream' collection capability has been declassified and publicly disclosed, certain other information regarding the capability remains currently and properly classified."
The EFF argued that the prior disclsoure of the NSA's Upstream capabilities made the information less sensitive.
On Friday, U.S. District Judge Rosemary Collyer noted that only the existence of the FISC opinion has been disclosed, and not the information contained in it.
She added that the opinion could be exempt from disclosure because its "specific content" never has been "officially and publicly disclosed."
The Justice Department did not respond to a request for comment.
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