LEGISLATION TO reform the National Security Agency’s surveillance of telephone metadata and put it on a firmer legal footing has passed the House with a huge bipartisan majority. President Obama backs it, as does a bipartisan majority in the Senate. The Senate would have passed the bill, too, but for the machinations of the majority leader, Mitch McConnell (R-Ky.), who favored an ill-considered perpetuation of the status quo.

For the fact that even the current, debatable legal basis of the NSA program has lapsed, at least temporarily, we have Mr. McConnell to thank — along with Kentucky’s other Republican senator. When Mr. McConnell finally allowed the reform compromise, known as the USA Freedom Act, to move Sunday, Rand Paul used procedural maneuvers to block a vote on it until at least Tuesday.

Mr. McConnell accused Mr. Paul, who’s running for president, of playing politics, which is true — up to a point. For Mr. Paul, opposition to NSA “spying” is a matter of libertarian principle bordering on passion. Indeed, the matter excites him so much that he has aimed extreme, sloppy rhetoric at those who don’t share his views, suggesting, for example, that “some people are so fearful” of terrorism that they believe “ISIS will be in every drug store in America, in every house, if we don’t get rid of the Constitution.”

Mr. Paul is the one misstating constitutional law. “[T]he phone records of law-abiding Americans are none of the government’s business!” his campaign Web site declares. Actually, the Supreme Court held 36 years ago that there is no constitutional right to privacy in phone records (as opposed to phone conversations). The court reasoned, realistically, that customers willingly convey numbers and times to the phone company each time they dial, knowing that the company retains the information for business purposes. Technology was more primitive in 1979; the justices may well decide that Fourth Amendment doctrine needs updating. Meanwhile, it is not tyrannical for government to rely on existing precedent.

Mr. Paul calls the NSA program “illegal,” which is somewhat more plausible, since the Bush and Obama administrations stretched the terms of the USA Patriot Act to win approval for it from the secret Foreign Intelligence Surveillance Court. If so, the cure is a new law, such as the one Mr. Paul just gratuitously blocked. The USA Freedom Act leaves metadata collection to the private sector, subject to searches approved by the intelligence court, but Mr. Paul thinks anything short of a warrant from an ordinary federal court would be unconstitutional. Again, he’s entitled to his opinion; again, it’s contrary to current Fourth Amendment law, as the legislation’s authors, senior Republicans and Democrats on the House and Senate Judiciary committees, well understand.

Denouncing fear and paranoia about terrorism, Mr. Paul sows fear and paranoia about government. Today, as always, the Constitution calls on us to balance liberty and security democratically. This is what the USA Freedom Act will do, just as soon as Mr. Paul stops grandstanding and lets his colleagues vote on it.