The Supreme Court handed down a brief order on Friday denying a request to block a federal ban on “bump stocks,” a device that effectively converts a semi-automatic rifle into a fully automatic weapon. These devices were banned by, of all institutions, the Trump administration after a bump stock was used in the 2017 Las Vegas mass shooting.

Yet, while even the Trump administration deemed these devices to be too dangerous for civilian use, two members of the Supreme Court would have blocked the ban. Both Justice Clarence Thomas and Neil Gorsuch voted to grant a request to stay a lower court decision allowing the ban to take effect.

Federal law generally bans “machineguns,” which are defined in the U.S. Code as “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.” A bump stock is a device that fits over the trigger and uses the momentum of the gun’s recoil to repeatedly pull the trigger after the shooter’s finger pulls the trigger just once.

To see a bump stock in action, watch this video.

The dispute in Damien v. Bureau of Alcohol, Tobacco, Firearms and Explosives hinges on whether bump stocks, which mimic a traditional machine gun but use an entirely different mechanism to achieve this result, fit within the legal definition of a “machinegun.”


As a federal appeals court, which also allowed the bump stock ban to take effect, noted in its opinion, the federal law governing machine guns is ambiguous. “The statutory phrase ‘single function of the trigger’ admits of more than one interpretation, for example. It could mean ‘a mechanical act of the trigger.’ Or it could mean ‘a single pull of the trigger from the perspective of the shooter.’”

The first interpretation would not include bump stocks, because these devices function by using the gun’s recoil to repeatedly pull its trigger. The second interpretation, however, would.

Under the Supreme Court’s decision in Chevron v. Natural Resources Defense Council, however, courts typically must defer to a regulatory agency’s interpretation of a federal statute, so long as that interpretation is reasonable. Thus, under Chevron, the ambiguity in the federal law should be resolved in favor of the administration, and the rule banning bump stocks should be upheld.

It is likely that Thomas and Gorsuch voted to block the rule as much because of their disdain for this Chevron decision as because of their desire to eliminate gun regulations. Both men have suggested that Chevron should be overruled. Should they get their way, which is increasingly likely as the Supreme Court moves to the right, that will give the conservative court much greater power to veto regulations its majority disapproves of.

For the time being, however, it appears that there are not five members of the Supreme Court who are willing to pick this fight over an especially dangerous weapon that was used in a particularly deadly mass shooting. Friday’s order means that the bump stock ban will take effect, at least temporarily, while the litigation challenging that ban proceeds.