WASHINGTON — Thirty-five years ago in United States v. Choate, the courts ruled that the Postal Service may record “mail cover,” i.e., what’s written on the outside of an envelope — the addresses of sender and receiver.

The National Security Agency’s recording of U.S. phone data does basically that with the telephone. It records who is calling whom — the outside of the envelope, as it were. The content of the conversation, however, is like the letter inside the envelope. It may not be opened without a court order.

The constitutional basis for this is simple: The Fourth Amendment protects against “unreasonable searches and seizures” and there is no reasonable expectation of privacy for what’s written on an envelope. It’s dropped in a public mailbox, read by workers at the collection center and read once again by the letter carrier. It’s already openly been shared, much as your phone records are shared with, recorded by, and (e)mailed back to you by a third party, namely the phone company.

Indeed, in 1979 the Supreme Court (Smith v. Maryland) made the point directly regarding the telephone: The expectation of privacy applies to the content of a call, not its record. There is therefore nothing constitutionally offensive about the newly revealed NSA data-mining program that seeks to identify terrorist networks through telephone-log pattern recognition.

But doesn’t the other NSA program — the spooky-sounding James Bond-evoking PRISM — give you the willies? Well, what we know thus far is that PRISM is designed to read the emails of non-U.S. citizens outside the United States. If an al-Qaeda operative in Yemen is emailing a potential recruit, it would be folly not to intercept it.

As former Attorney General Michael Mukasey explains, the Constitution is not a treaty with the rest of the world; it’s an instrument for the protection of the American citizenry. And reading other people’s mail is something countries do to protect themselves. It’s called spying.

Is that really shocking?

The problem here is not constitutionality. It’s practicality. Legally this is fairly straightforward. But between intent and execution lies a shadow — the human factor, the possibility of abuse. And because of the scope and power of the NSA, any abuse would have major consequences for civil liberties.

The real issue is safeguards. We could start by asking how an Edward Snowden, undereducated, newly employed, rootless and grandiose, could have been given such access and power. We need a toughening of both congressional oversight and judicial review, perhaps even some independent outside scrutiny. Plus periodic legislative revision — say, reauthorization every four years — in the light of efficacy of the safeguards and the nature of the external threat.

The object is not to abolish these vital programs. It’s to fix them. Not exactly easy to do amid the current state of national agitation — provoked largely because such intrusive programs require a measure of trust in government and this administration has forfeited that trust amid an unfolding series of scandals and a basic problem with truth-telling.

There are nonetheless two other reasons these revelations have sparked such anxiety. Every spying program is a compromise between liberty and security. Yet here is a president who campaigned on the proposition that he would transcend such pedestrian considerations. “We reject as false the choice between our safety and our ideals,” he declared in his first inaugural address, no less.

When caught with his hand on your phone data, however, President Obama offered this defense: “You can’t have 100 percent security and also then have 100 percent privacy. … We’re going to have to make some choices as a society.”

So it wasn’t such a false choice after all, was it, Mr. President?

Nor does it help that just three weeks ago the president issued a major foreign-policy manifesto whose essential theme was that the War on Terror is drawing to a close and its very legal underpinning, the September 2001 Authorization for Use of Military Force, should be not just reformed but repealed to prevent “keeping America on a perpetual wartime footing.”

Now it turns out that Obama’s government was simultaneously running a massive, secret anti-terror intelligence operation. But if the tide of war is receding, why this vast, ever-expanding NSA dragnet whose only justification is an outside threat — that you assure us is ever receding?

Which is it, Mr. President? Tell it straight. We are a nation of grown-ups. We can make choices. Even one it took you four years to admit is not “false.”

Charles Krauthammer is a syndicated columnist. Talk back at letterstoeditor@bostonherald.com.