It’s a great idea to ban terrorists and suspected terrorists from buying firearms, but the U.S. government’s “No Fly List” can’t be used to do it.

The problem is that the no-fly list is secret. The government won’t say who’s on it, or how they got on it, or how they can get off it.

“The U.S. government does not reveal whether a particular person is on or not on a watchlist,” the Department of Homeland Security explains on its website. “If the government revealed this information, terrorist organizations would be able to circumvent the watchlist’s purpose by determining in advance which of their members were likely to be questioned or detained.”

That means the use of the no-fly list for gun sales might actually be helpful to terrorists, but there’s an even more serious problem with the idea. It crumbles the foundation of all your constitutional rights: due process of law. 

The U.S. Constitution twice guarantees due process of law to every person. It’s in the Fifth and Fourteenth Amendments. But what does it mean, exactly?

At the time of the founding of the nation, “due process” meant the ordinary procedures of the law, the opposite of arbitrary power.

In our era, the U.S. Supreme Court has given “due process” a broader meaning. The term now encompasses a general right to fundamental fairness.

But by either definition, the government can’t deny a basic constitutional right to any person just by placing them on a secret government list.

The no-fly list is a subset of the U.S. government’s terrorist watchlist, which is administered by the FBI and the Justice Department in cooperation with the Departments of Homeland Security, Defense, State and Treasury, and the Central Intelligence Agency.

According to the DHS website, “Intelligence and law enforcement agencies nominate individuals for the watchlist based on established criteria.”

What criteria? Established by whom? We don’t know and they’re not going to tell us, and that’s fine for a screening tool to prevent some passengers from boarding planes. There is no explicit constitutional right to travel on commercial flights.

But there certainly is a constitutional right to keep and bear arms. In order for the government’s terrorist watchlist to be used as the basis for limiting that right, it will have to be made public. Otherwise, innocent people will be denied their rights based on mistakes, like the ones DHS is trying to sort out with its Traveler Redress Inquiry Program.

“Many people erroneously believe that they are experiencing a screening delay because they are on a watchlist,” DHS says on its website. “In fact, such delays are often caused merely by a name similarity to another person who is on the watchlist. Ninety-nine percent of individuals who apply for redress are not on the terrorist watchlist, but are misidentified as people who are.”

With an error rate that high, the government’s use of the watchlist must be watched.

President Obama called it “insane” that people on the no-fly list can buy guns, and Ohio Gov. John Kasich, a Republican presidential candidate, agreed with him. But it’s not insane to protect innocent people from secret government actions against them.

Limits on government power are what make the United States a free country. In other places, officials can simply decide to do anything, to anybody, at any time, for any reason. Not here.

Americans have rights that cannot be taken away by the arbitrary actions of government officials.

That’s the deal we signed, and we’re going to hold them to it.