Which, of course, is another way of saying that they don't have the letter of the law on their side. The Supreme Court is set to hear oral arguments in Cargill v. Garland on Wednesday, and the fundamental question before the Court is whether a bump stock device is a “machinegun” as defined in 26 U.S.C. 5845(b) because it is designed and intended for use in converting a rifle into a machinegun, which, under federal law, is “any weapon which shoots, is designed to shoot, or can be readily restored to shoot, automatically more than one shot, without manual reloading, by a single function of the trigger.”

For years the ATF approved bump stocks for sale, but after the Route 91 festival shooting in Las Vegas in 2017, the agency reversed course and banned the product, declaring that its prior determinations did “not reflect the best interpretation of the term ‘machinegun.’ The ATF concluded that the phrase “single function of the trigger" also encompasses a “‘single pull of the trigger,’” and even "motions 'analogous' to a single pull; an argument persuasive to a couple of federal appellate courts, but not the Fifth Circuit, which ruled that the ATF's new definition stretched far beyond what the federal statute in question actually says. 

Ahead of Wednesday's court hearing, both sides are using the press to make their case, with ABC News set to run a report on bump stocks on Primetime Live tonight. The network spoke to Michael Cargill, who's leading the charge to have the ATF's current rules overturned, along with bump stock creator Jeremiah Cottle, survivors of the Las Vegas shooting, and several gun control activists who inadvertently helped demonstrate the weakness of the government's argument. 

Steve Kling, a retired Army commander of a small arms training unit and a gun safety advocate for the Giffords organization, said ATF's reversal reflects a more accurate analysis of federal law.

"The spirit of the law is to prevent automatic weapons, weapons that have a significant cyclical rate of fire, from being on our streets and possessed by just anyone," he said.

"I've fired a lot of automatic weapons, including ones with bump stocks. There's no question that they're fun. It's fun to drive a supercar at 180 miles an hour down a highway. But we don't allow that either," Kling said.

Again, a firearm equipped with a bump stock isn't an "automatic" weapon, no matter how much Kling believes otherwise. And while we may not allow drivers to go 180 mph, we also don't ban cars that can go that fast (though California lawmakers are giving it their best shot).  

That doesn't mean that bump stocks can't be banned, but doing so would require congressional action, not an executive branch agency deciding to re-interpret the plain language of the National Firearms Act in order to retroactively prohibit the possession of a lawfully purchased and possessed product. 

Michael Cargill, an Army veteran and owner of Central Texas Gun Works outside Austin, cleared his store shelves of bump stocks after the ATF imposed the 2018 ban and surrendered two he owned himself. But he sued the agency in federal court and is leading the fight to get the devices back.

"This is a product that I legally purchased and had it in the store," Cargill said in an interview at his shop, "and all of a sudden an agency within the federal government decided they're going to ban this particular product. I said, 'This is crazy, this is not the America that I know. We've got to do something about this.'" 

Cargill insists a bump stock is a firearm accessory that does not render a semi-automatic weapon fully automatic and that the ATF overstepped its authority. He's now asking the Supreme Court to strike down the agency's ban.

"We need to follow the laws that we already have right now and not venture past that point," Cargill said. "An agency within the federal government can't come out and actually turn millions of people into felons overnight or ban a product. We have to go to Congress to do that."

As the National Shooting Sports Foundation argued in its amicus brief in Cargill, the bump stock ban is hardly the only example of ATF overreach in recent year. 

Time and again in recent years, ATF has executed similar about-faces in service of restricting access tofirearms with features it had previously recognized to be legal. The agency has tried to justify those efforts by taking an increasingly broad view of the “purpose” of the federal statutes setting forth its important but limited mission and an increasingly narrow view of the constraints that those statutes impose. Making matters worse, ATF has largely given the Second Amendment the back of the hand, imposing novel firearms restrictions without seriously grappling with constitutional text or historical tradition. The agency is in dire need of a reminder that it is not for ATF to decide which arms the people may keep and bear.

If the Court upholds the ATF's action here, the decision could not only have implications for the agency's more recent rules on unfinished frames and receivers and pistol stabilizing braces, but would give the green light for the ATF to rewrite entire sections of the NFA and Gun Control Act to create a host of new gun control laws without a vote in Congress. This case is hugely important, not only for the hundreds of thousands of people who lawfully purchased bump stocks in the past, but for every gun owner in the country going forward. Gun control activists may believe that the spirit of the law is on their side, but if SCOTUS remains true to the letter of the law, which they're supposed to do, then I don't think they have any choice but to strike down the ATF's rule and remind the agency that it's the role of Congress to create new law, not government agencies.