The Court of Appeals for the District of Columbia has overturned an injunction against the US government's phone surveillance program. Today, the court handed down a decision in Klayman v. Obama, a lawsuit arguing that the NSA's mass collection of phone records is unconstitutional. It found that there was not enough evidence that the lawsuit's subjects were actually under surveillance, reversing a decision made in late 2013.

The court didn't address whether the surveillance program was legal or constitutional. Instead, it concluded that the case's subjects lacked standing to bring a complaint at all, because they were unable to demonstrate that they'd suffered harm. The secrecy of US surveillance programs has made it almost impossible to prove that a specific person or organization was subject to them, so Klayman and other recent cases have relied on leaked documents from Edward Snowden, particularly a court order requiring Verizon Business Services to hand over metadata on all its customers' calls.

"It is only possible — not substantially likely — that their own call records were collected."

This has been shaky legal territory, but a 2013 federal decision found it convincing enough to order the NSA to temporarily stop collecting data on the case's two plaintiffs. This order was delayed while the government responded, and the appeals court says it shouldn't have been issued at all. Judge Janice Rogers Brown writes that "plaintiffs have demonstrated it is only possible — not substantially likely — that their own call records were collected," not meeting the burden of proof for an injunction. Though one judge called for the case to be totally dismissed, it's been handed back to a lower court.

While this case has suffered a setback, the ACLU got a more favorable decision in a similar case earlier this year, when a New York appeals court found the program illegal. But because Congress has already ordered a limited reform of the NSA's surveillance program, which will take place later this year, the court stopped short of suspending it. The ACLU has since filed a motion to end the program immediately.