The government's go-to excuse for shielding its surveillance programs its also its most foolproof. We can't tell you about our programs — or if they even exist — they argue, because to do so would put our national security at risk. On Monday, a federal judge dealt that argument a significant blow — in one lawsuit, anyway.

That suit was filed in 2008 by the Electronic Frontier Foundation following revelations from whistleblower Mark Klein about the National Security Agency tapping AT&T's network traffic in San Francisco. Over the ensuing five years, the state blocked EFF's lawsuit aimed at halting the spying. Eventually, the government resorted to the invocation of "state secrets privilege," the argument that disclosing evidence related to the case (e.g., the existence of the wiretapping Klein reported) would itself constitute a threat to national security.

On Monday, Judge Jeffrey White of the District Court of Northern California agreed with the EFF that the government's state secrets claim in this lawsuit should be rejected. If you'd like to read the full order, go for it. Not being legal experts, though, we spoke with EFF senior staff attorney Lee Tien, who explained the implications and next steps. State secrets claims, Tien said, have been "a very powerful weapon for the government to block certain lawsuits." He gave an example. If the government is prosecuting you using surveillance that you don't know how it got, even if you ask for it, you might not see the evidence against you. "Normally, the government can be like, 'tough shit,'" he said.

But when Congress passed the Foreign Intelligence Surveillance Act, it included a system for bypassing state secrets claims. FISA's section 1806(f) allows a presiding judge to consider secret evidence and determine whether or not it is legal — without making that evidence public. If practical, the judge could allow the defendant's counsel to participate in arguments, though Tien notes this rarely happens. "The point is that under the FISA procedure, the government has to submit documents that the judge can consider." Without the FISA option, the EFF notes, "the government could potentially violate the law and Constitution as it sees fit, and—just by stamping 'STATE SECRET' on the top of their actions—those injured by their actions would be denied justice." In many cases, it's done essentially that.

The court's decision doesn't mean that the next step is judicial review of the evidence of NSA wiretaps in San Francisco. The government can challenge it, for example. And both sides will return to court in August to answer questions posed by the judge.

One of which is how the government wants to proceed. Following the Edward Snowden leaks, after all, it's in an awkward position. "Every time there's a new leak," Tien said, "the world changes as far as the level of secrecy around a particular thing, and there are all these ripple effects." When evidence of PRISM was revealed, for example, the government had to assess if it would acknowledge details of the leak, which other components of its electronic surveillance was at risk, and so on. "Even though something is out, they haven't figured out what they have to say — what the logically have to say, what they politically want to say."

Which is one of the reasons that yesterday's legal determination that the NSA's surveillance processes can't rely on state secrets claims probably won't itself have immediate, broader legal implications. The agency has replied to some Freedom of Information Act requests refusing to confirm or deny the existence of individual citizens' phone metadata, for example. And technically, Tien points out, the only information acknowledged by the government stemmed from Snowden's leak: a ninety-day collection of data from Verizon. The government is still figuring out where the lines on this are drawn. "I think we're still in kind of a flux-y period as the governement is trying to figure out how to have a coherent position on the effects of the Snowden leaks," Tien said. This decision doesn't kick any doors open.

Nor does Tien think Snowden's leaks were key to the decision. "The legal argument" for rejecting a state secrets claim "has always been a very solid," he said, "since two things about it sort of makes no sense. One, it's crazy to think that Congress can't do something that affects the privilege." The FISA legislation came in 1978; the Supreme Court decision on secrets was in the 1950s. "Two, the way the statute is set up to allow this very specific procedure," which clearly trumps that sort of protection.

"I think there are more legal questions coming down the pike," Tien said. If revelations about the NSA's activity continue, that will probably end up an understatement.

Photo: NSA chief Keith Alexander, testifying before Congress last month. (AP)