A federal judge ordered the government's bulk phone spying program shut down immediately, calling it likely unconstitutional, in a symbolic victory for critics of a program set to expire in three weeks.
Judge Richard Leon issued the order in a long-running case as the National Security Agency was preparing to shutter its "bulk telephone metadata" collection program November 29.
Leon said in a 43-page opinion that even though the program is being winded down, he ordered an injunction "because the loss of constitutional freedoms for even one day is a significant harm."
Leon also noted that "this case is perhaps the last chapter in the Judiciary’s evaluation of this particular Program’s compatibility with the Constitution."
The impact of the ruling was not immediately clear. The U.S. Justice Department did not reply to requests for comment.
Last month, an appeals court declined to order a halt to the program in a separate legal action.
Congress has allowed bulk telephone data -- the subject of leaks by former intelligence contractor Edward Snowden -- to continue until a 180-day transition period expires on November 29.
After that, the USA Freedom Act prohibits the National Security Agency (NSA) from conducting mass surveillance, although the agency will be allowed to retain records for litigation purposes.
Elizabeth Goitein, co-director of the New York University Brennan Center's Liberty and National Security Program, said the latest ruling was "a testament to the importance of the rule of law."
"This is an illegal program that violates the privacy of millions of Americans. It should not continue for another minute, let alone another three weeks," she said in a statement.
But Goitein acknowledged that a government appeal would most likely result in a stay, or postponement of the order "that would effectively run out the clock."
The case was filed by Larry Klayman of the activist group Freedom Watch and was among several cases filed challenging the legality of the bulk surveillance disclosed in Snowden's leaked documents.