Privacy advocates looking to drag federal surveillance programs before a public court notched a key win Tuesday after a federal appeals court resurrected Wikimedia's lawsuit against the NSA.

The ruling by the U.S. Court of Appeals for the Fourth Circuit allows Wikimedia, represented by lawyers from the American Civil Liberties Union and Knight First Amendment Institute at Columbia University, to argue the merits of its case in a public courtroom. A Maryland district court dismissed the case in 2015, agreeing with the government's position that the plaintiffs lacked standing because their allegations were speculative.

While Judges Albert Diaz, Diana Motz and Andre Davis agreed Wikimedia has standing, the court ruled the other plaintiffs, which include Amnesty International and The Nation magazine, cannot move forward. Davis dissented on that point, arguing that those plaintiffs do have standing, but that his colleagues need not even go as far as to decide that given the conclusion on Wikimedia.

The key factor in Wikimedia prevailing was its detailed description of how it believes the National Security Agency is intercepting its emails based on current rules for how the internet works.

“Wikimedia has plausibly alleged that its communications travel all of the roads that a communication can take, and that the NSA seizes all of the communications along at least one of those roads,” Diaz wrote. “Thus, at least at this stage of the litigation, Wikimedia has standing to sue for a violation of the Fourth Amendment. And, because Wikimedia has self-censored its speech and sometimes forgone electronic communications in response to Upstream surveillance, it also has standing to sue for a violation of the First Amendment.”

The Justice Department and NSA declined to comment.

Ashley Gorski, an ACLU staff attorney, said the decision is a “landmark victory for Wikimedia.” The government has “continually” sought procedural barriers to stop these types of cases by arguing that standing or the state secrets doctrine preclude any litigation.

“I think what's really important here is that there's going to be public judicial scrutiny — scrutiny in public courts — of these surveillance programs,” Gorski said.

Tuesday's ruling is the second setback in two weeks for the government. Just last week, a California district court ordered the government to provide evidence in a case brought on behalf of AT&T customers who claim the NSA is illegally surveilling them. The government has opposed such a disclosure.

Tuesday's case concerns the NSA's “Upstream” surveillance program, which is authorized under Section 702 of the 2008 FISA Amendments Act. The program, geared toward fighting terrorism and other foreign threats, allows the agency to review internet communications from people outside the U.S. even if they're communicating with someone inside the country. Wikimedia claims the NSA does this by monitoring the main cables of the internet used to transfer data, which together make up the “internet backbone.”

Wikimedia claims data such as an email sent from one end of a cable is broken down into multiple bite-sized packets and reassembled at the receiving end. This means the NSA has to gather all the packets going across various cables, reassemble the messages and then sift through the contents.

Wikimedia argued the “sheer volume of [its] communications makes it virtually certain that the NSA has intercepted, copied, and reviewed at least some of [its] communications.” The organization estimated it engages in more than 1 trillion international communications each year, with people located “in virtually every country on earth.”

The case is an example of how lower courts have struggled in the wake of two Supreme Court rulings, the 2013 decision in Clapper v. Amnesty International USA and last year's Spokeo v. Robbins, to determine standing in privacy cases.

The district judge who dismissed the Wikimedia case relied on the Clapper decision, which held that Amnesty International's allegations were too speculative to establish standing. However, shortly after that decision, Edward Snowden notoriously leaked details of NSA surveillance programs, allowing Wikimedia to show more detail about how the surveillance process works. Thus, the court said Clapper couldn't control this case.

“There's nothing speculative about it—the interception of Wikimedia's communications is an actual injury that has already occurred,” Tuesday's decision said.

Marc Rotenberg, president of the Electronic Privacy Information Center, said electronic privacy cases generally pose “unique” standing challenges because it can be difficult to determine when an actual privacy violation occurs.

“I think [the decision] does represent a growing understanding among the federal courts about the nature of privacy harm,” Rotenberg said.

Rotenberg added the Spokeo decision complicates matters further because the Supreme Court held plaintiffs must show an “injury in fact” to have standing. That's defined as “the invasion of a legally protected interest that is concrete and particularized and actual or imminent.” Not exactly clear-cut, Rotenberg pointed out.

“When you combine the difficult road that privacy claimants face with the lack of clarity that the court left in Spokeo, it's becoming increasingly important to clarify the circumstances under which you can bring privacy lawsuit,” he said.

Cogan Schneier covers litigation in Washington, D.C., for the National Law Journal and Law.com. Contact her at [email protected]. On Twitter: @CoganSchneier.