I think there is a fair chance that the U.S. Court of Appeals will overturn yesterday’s order by U.S. District Judge Richard J. Leon that the National Security Agency halt its telephone metadata collection program and destroy its existing records. Leon’s preliminary injunction, handed down in an angry opinion in the case, Klayman vs. Obama, orders President Obama’s administration to end the program within six months unless a higher court should reverse him.

What has already gained attention — quite properly — is the judge’s refusal to follow Smith vs. Maryland, a 1979 Supreme Court decision holding that citizens lack a reasonable expectation of privacy as to the list (as against the content) of their phone calls. So settled and accepted is Smith that legal experts routinely assert that “it is well established that individuals do not have an expectation of privacy in the phone numbers they call.”

But Leon isn’t so sure. The majority that decided that case, he writes, could never have imagined “how the citizens of 2013 would interact with their phones.” In particular, “the almost-Orwellian technology that enables the Government to store and analyze the phone metadata of every telephone user in the United States is unlike anything that could have been conceived in 1979.”

Although the rejection of Smith has the blogosphere buzzing, an equally striking feature of Leon’s opinion is buried in the footnotes: his focus on how much the Obama administration has kept from his view. Leon tells us in footnote 56, for example, that the pleadings do not disclose whether the NSA program collects data on text messages. (He estimates that Americans send 6 billion texts a day.) Footnote 57 explains that he cannot tell from the pleadings whether the government collects location information along with numbers called — a practice that would raise particular privacy problems of its own.

Most important, Leon challenges the contention by the program’s supporters that the data collection has thwarted actual terrorist plots: “Although the Government has publicly asserted that the NSA’s surveillance programs have prevented fifty-four terrorist attacks, no proof of that has been put before me” (that’s footnote 65). He quotes Senator Patrick Leahy, Democrat of Vermont, as saying, “These weren’t all plots and they weren’t all thwarted” — and points out that the government could have filed sealed evidence of the program’s success but chose not to do so.

These are serious challenges. The principal political argument in support of the metadata program and its equally controversial cousins is its crucial role in protecting the American people. In a free society, there comes a point at which a government charged with violating the privacy of its citizens can no longer rely on secret evidence and a plea for trust.

Given my obvious sympathy with the privacy claims, why do I think there’s a good chance that the decision will be overturned? For one thing, an appellate court might reasonably decide that the plaintiffs lack standing, unless they can show that their own telephone records have been not only seized without a warrant but also searched. Not for nothing have the NSA and its lawyers devised the two-step process in which it stores the records regularly but maintains internal restrictions on searching them.

And although Leon’s opinion makes a persuasive if rhetorically overheated argument that the world has changed in the years since Smith vs. Maryland, an appellate panel might reasonably decide that the matter of whether societal or technological evolution renders a Supreme Court precedent outdated is a question for the Supreme Court.

Still, whatever happens on appeal, the gauntlet has been thrown down. And high time. The war on terror is far from over, and there remain those in the world who want to kill Americans because they are Americans. But it doesn’t follow that all means of pressing the battle are appropriate. Gabriel Garcia Marquez famously noted that we live three lives: one public, one private, one secret. There ought to be a way to fight the war on terror without the need for the government to assert ownership over all three.