In the latest setback for the NSA, a federal judge ruled on Monday that the spy agency's phone metadata collection program, which gathers information on calls to, from, and within the United States, probably violates the Constitution.

Calling the practice "indiscriminate" and an "arbitrary invasion" of privacy, U.S. District Court Judge Richard Leon wrote that a lawsuit brought by conservative activist Larry Klayman had standing to continue and would likely lead to the NSA's program being struck down for violating the Fourth Amendment.

From Politico:

"Plaintiffs have a very significant expectation of privacy in an aggregated collection of their telephone metadata covering the last five years, and the NSA's Bulk Telephony Metadata Program significantly intrudes on that expectation," wrote Leon, an appointee of President George W. Bush. "I have significant doubts about the efficacy of the metadata collection program as a means of conducting time-sensitive investigations in cases involving imminent threats of terrorism."

Leon issued a preliminary injunction banning the NSA from collecting data on the Verizon accounts of Klayman and one of his clients, though the order was stayed to allow for an appeal.

As the Wire points out, the ruling could lead to the end of the NSA's metadata collection, which is already facing challenges from Congress and the White House.

Monday's ruling — even though its judgment is stayed pending an appeal — will provide ammunition to those who've sought to eliminate the NSA's ability to collect phone metadata. There are multiple bills before Congress right now that would refine the Patriot Act's Section 215 to eliminate the ability to collect this information; President Obama's own panel recommending reforms will apparently offer some restrictions on the practice.

UPDATE: Edward Snowden released a statement on the ruling. From the New York Times:

In a statement distributed by the journalist Glenn Greenwald, who was a recipient of leaked documents from Mr. Snowden and who wrote the first article about the bulk data collection, Mr. Snowden hailed the ruling.

"I acted on my belief that the N.S.A.'s mass surveillance programs would not withstand a constitutional challenge, and that the American public deserved a chance to see these issues determined by open courts," Mr. Snowden said. "Today, a secret program authorized by a secret court was, when exposed to the light of day, found to violate Americans' rights. It is the first of many."

[Image via AP]