A federal judge has ruled that the National Security Agency's controversial phone metadata collection is likely unconstitutional and has ordered an immediate stop to the program. Though the decision comes as the NSA's program, in its current form, is set to expire in weeks, the ruling sets an important precedent for privacy rights.

In the 43 page ruling filed on Monday, U.S. Circuit Court Judge Richard Leon said the NSA's bulk metadata collection program "likely violates the constitution," violating the Fourth Amendment, which prohibits unreasonable searches and seizures by the government. The ruling was a victory for the plaintiff Larry Klayman, a conservative legal activist who challenged the federal government's collection of his and his co-plaintiff's phone records.

The practical effect of the decision is minimal: the NSA has been ordered to stop collecting Klayman's co-plaintiff's phone records through Verizon's business network services. But as a result of Congress passing the USA Freedom Act in the summer, the NSA was already going to change its surveillance operating procedures by Nov. 29.  

As the New York Times reported, Leon acknowledged the short-term and minimal practical effect of his ruling, but stressed that his judgment was about more than ordering an injunction against collection of a few plaintiff's phone records.

"With the government's authority to operate the bulk telephony metadata program quickly coming to an end, this case is perhaps the last chapter in the judiciary's evaluation of this particular program's compatibility with the constitution," wrote Judge Leon in his decision. "It will not, however, be the last chapter in the ongoing struggle to balance privacy rights and national security interests under our Constitution in an age of evolving technological wizardry."

The decision in Klayman v. Obama sets a precedent that civil liberties groups are hailing as immensely important. One such group, the Electronic Frontier Foundation, wrote, "Judge Leon's opinion and his refutation of the government's arguments, which are almost identical to the government's arguments in other mass surveillance cases, should be broadly influential in ongoing and future challenges to the NSA's suspicion-less spying."

Previous court decisions have gone as saying that the NSA's telephone metadata program was not legal under the Patriot Act and went far outside the bounds of the authority granted by the legislature.

But as we previously reported, in that case, ACLU v. Clapper, the judge refrained from making any decisions on its constitutionality. Just before Congress passed the USA Freedom Act, Second Circuit Court of Appeals Judge Gerard Lynch stated the metadata program "exceeds the scope of what Congress has authorized" but also wrote, "We reiterate that, just as we do not here address the constitutionality of the program as it currently exists, we do not purport to express any views on the constitutionality of any alternative version of the program."

In contrast, Leon's ruling on Monday could have an impact on future surveillance programs, as it is in opposition to a Supreme Court precedent set in 1979, which held that telephone call logs, what's now called metadata, was not protected by the Fourth Amendment. Leon argued that the vastly expanded technological capability in modern times, what he called "technological wizardry," had brought metadata into the scope of the privacy protections afforded by the Fourth Amendment.

The Justice Department told the New York Times it was reviewing the decision, but had no comment on whether it would appeal the injunction.