The National Rifle Association may not be opposed to at least one gun control measure circulating after the Las Vegas shooting, in which a gunman killed 59 people, including himself, and injured hundreds of others.

On Thursday, the NRA put out a statement calling on the federal government to review modifications reportedly used by the Las Vegas gunman, Stephen Paddock:

Despite the fact that the Obama administration approved the sale of bump fire stocks on at least two occasions, the National Rifle Association is calling on the Bureau of Alcohol, Tobacco, Firearms, and Explosives (BATFE) to immediately review whether these devices comply with federal law. The NRA believes that devices designed to allow semi-automatic rifles to function like fully-automatic rifles should be subject to additional regulations.

The NRA goes on to clarify that it still believes Congress should loosen gun laws — by guaranteeing a right to carry — to “allow law-abiding Americans to defend themselves and their families from acts of violence.”

Traditionally, semiautomatic and automatic weapons are supposed to function very differently. Automatic weapons are what many Americans think of as machine guns; these are guns that can continuously fire off a stream of bullets by simply holding down the trigger, making them very deadly. Semiautomatic weapons, by contrast, fire a single bullet per trigger pull. The difference between an automatic and a semiautomatic effectively translates to firing hundreds of rounds a minute versus dozens or so in the same time frame.

But bump fire stocks, which the NRA refers to, can change semiautomatic weapons to effectively function like automatic ones. The Associated Press explained:

The device basically replaces the gun's shoulder rest, with a "support step" that covers the trigger opening. By holding the pistol grip with one hand and pushing forward on the barrel with the other, the shooter's finger comes in contact with the trigger. The recoil causes the gun to buck back and forth, "bumping" the trigger. Technically, that means the finger is pulling the trigger for each round fired, keeping the weapon a legal semi-automatic.

Police found 12 bump stocks among Paddock’s arsenal of 23 guns in the hotel room from which he shot people.

These devices are generally legal. Miles Kohrman at the Trace reported that the ATF gave one company, Bump Fire System, a letter of approval before its product shipped to market in 2012. And the ATF reaffirmed as much in a statement a couple days ago, suggesting that yet another review, like the NRA calls for, may not do much good.

It’s also just one kind of modification. There are others, including a crank that replaces the trigger — turning a gun into what a gun aficionado channel on YouTube called “a mini Gatling gun.” And it’s still possible to make illegal modifications that turn guns into fully automatic weapons, as Andy Greenberg explained at Wired.

“Converting a semi-automatic to fully automatic is very, very easy,” John Sullivan, lead engineer for the gun access group Defense Distributed, told Wired. “At the end of the day, machine guns are easy to make.”

Like other loopholes in gun laws, these have been in large part buttressed by the typical pro-gun argument that people should have these weapons to be able to defend themselves and their families. But the research suggests that owning a gun actually increases the risk of death.

Still, even the NRA seems skeptical about these modifications. The group actually bans them from its own firing range at NRA headquarters, due to safety concerns, Lorraine Woellert reported for Politico.

Sen. Dianne Feinstein (D-CA) recently put forward a bill that would ban these types of modifications. But she proposed a similar bill in 2013 after the Sandy Hook Elementary School shooting in Newtown, Connecticut — and it never even got a vote.

For more on America’s gun problem, read Vox’s explainer.