The following editorial appeared in the Dec. 30 Wall Street Journal:

Well, what do you know. Maybe the National Security Agency's collection of telephone metadata doesn't violate the Fourth Amendment or any relevant statute. You wouldn't know this from the left-libertarian political clamor of recent weeks, but on Friday federal Judge William Pauley delivered a much-needed reality check.

Judge Pauley, a Bill Clinton appointee, rebuffed a challenge from the American Civil Liberties Union and ruled that the program to "find and isolate gossamer contacts among suspected terrorists in an ocean of seemingly disconnected data" is critical for national security in the modern era. Unlike Judge Richard Leon's mid-December opinion against antiterror surveillance that made him a shooting political star, Judge Pauley grounded his careful decision in the Constitution and Supreme Court precedent.

Since Smith v. Maryland in 1979, the High Court has held that individuals have no "reasonable expectation of privacy" about numbers they dial or receive. When someone voluntarily conveys information to a third party, "he forfeits his right to privacy in the information," Judge Pauley observes. Phones have "more versatility" since Smith, and the scope of collection is broader, yet "what metadata is has not changed over time."

Reports of the death of this legal doctrine are greatly exaggerated. The Fourth Amendment is designed to balance liberty and security, and expanding privacy to include such third-party information would disrupt the equilibrium. Rather than forums for terrorists to share and expose their intentions, the telecoms would become safe houses for them to conspire. Warrants might be impossible because evidence would be protected by the Fourth Amendment.

The ACLU argued that metadata collection is too broad and sweeps up irrelevant information, conjuring government spooks rifling through digital drawers. But Judge Pauley writes that the uses of the bulk collection program are narrow, only relevant information is reviewed by the NSA, and it is overseen by all three branches of government.

His opinion is also a tutorial for the privacy scolds about the realities of counterterrorism. The metadata program is not meant to procure evidence to prove wrongdoing after the fact, like ordinary law enforcement. The point is to "detect relationships so attenuated and ephemeral they would otherwise escape notice" and stop attacks, and there is no way to know prospectively which metadata contain useful information. "This blunt tool only works because it collects everything. . . . Without all the data points, the Government cannot be certain it has connected the pertinent ones," Judge Pauley writes.

He then runs down some of the plots that metadata collection helped prevent, such as New York City subway bomber Najibullah Zazi. Then there's the plot that wasn't prevented, as Judge Pauley describes:

"Prior to the Sept. 11 attacks, the National Security Agency intercepted seven calls made by hijacker Khalid al-Mihdhar, who was living in San Diego, California, to an al Qaeda safe house in Yemen. The NSA intercepted those calls using overseas signals intelligence capabilities that could not capture al-Mihdhar's telephone number identifier. Without that identifier, NSA analysts concluded mistakenly that al-Mihdhar was overseas and not in the United States. Telephony metadata would have furnished the missing information and might have permitted the NSA to notify the Federal Bureau of Investigation of the fact."

Judge Pauley's unfashionable opinion won't earn him the media acclaim of Judge Leon, but it is a useful corrective for our current political amnesia. This controversy seems bound for the Supreme Court, and Judge Pauley's ruling is a worthy amicus brief.