AS PRESIDENT OBAMA said in brief but eloquent remarks Friday, there is no rational explanation for the massacre that occurred in a Colorado movie theater early Friday.

Such violence, such evil, is senseless. It’s beyond reason,” Mr. Obama said. “And if there’s anything to take away from this tragedy it’s the reminder that life is very fragile. Our time here is limited, and it is precious. And what matters at the end of the day is not the small things, it’s not the trivial things, which so often consume us and our daily lives. Ultimately, it’s how we choose to treat one another and how we love one another.”

There’s something else that is senseless, though, and that is America’s gun laws. The temptation is not to mention this fact. That’s true partly because, as E.J. Dionne Jr. points out on the opposite page today, any mention of gun control is dismissed by gun-control opponents as an “exploitation” of tragedy.

But it’s true also because we’ve all been worn down by the futility and repetitiveness of the debate. A massacre occurs; advocates of gun control point out the folly of total permissiveness; the laws do not change; the issue disappears until the next massacre.

Well, we plead guilty to repeating ourselves. There is no rational basis for allowing ordinary Americans to purchase assault rifles. They’re not necessary for hunting, and they’re not needed for self-defense.

The alleged shooter in Friday’s crime, which claimed at least 12 lives, came to the theater with two .40-caliber Glock handguns, a Remington 12-gauge shotgun and a Smith & Wesson AR-15 assault-style rifle. According to NBC News, “the weapons were legally bought from local stores of two national chains — Gander Mountain Guns and Bass Pro Shop — beginning in May.”

Yes, the Second Amendment protects a citizen’s right to own a gun, but it does not preclude reasonable regulation for public safety. Yes, mass killings occur in societies with stronger gun laws, but not with such regularity — and not against the backdrop of daily gun violence, both criminal and accidental, that distinguishes the United States.

We don’t expect this massacre to lead to more sensible laws. We understand the politics. Still, it’s disappointing that the president doesn’t couple his words of comfort with some reminder of the common-sense regulation that could make such tragedies less common. The politics of guns will never shift if people are too cowed or dispirited even to join the argument.

U.S. gun laws make no sense.