A device called a "bump stock" is attached to a semi-automatic rifle at the Gun Vault store and shooting range in South Jordan, Utah. Credit: Rick Bowmer | AP

A federal judge in Washington ruled late Monday that the Trump administration’s ban on rapid-fire rifle attachments known as bump stocks can move forward, stymieing efforts by gun-rights groups that sought to block the new policy.

In a 64-page decision, U.S. District Judge Dabney L. Friedrich found that the Firearms Policy Coalition and other groups did not put forth any convincing legal arguments in favor of stopping the Trump administration from carrying out the ban, which targets a device used in the 2017 Las Vegas massacre, the deadliest mass shooting in modern U.S. history.

Friedrich, a 2017 appointee of President Trump to the District of Columbia, ruled it was “reasonable” of the Bureau of Alcohol, Tobacco, Firearms and Explosives to conclude that a bump-stock, which uses the recoil energy from a rifle to automatically fire the next round, performs the same function as a machine gun and should therefore be banned just like machine guns under federal law.

Trump moved to ban bump stocks in the wake of the Las Vegas shooting with loud bipartisan support from Congress and anti-gun-violence advocates. The October 2017 shooting left 58 people dead and hundreds wounded after a man rained gunfire on concertgoers at the Route 91 Harvest Festival, firing from the 32nd floor of his Vegas hotel. Affixed to a dozen of the 23 rifles found in his room were bump stock devices, which allowed him to fire multiple rounds more quickly.

The Firearms Policy Coalition sued the Trump administration in December after ATF changed federal rules to ban the devices at Trump’s request. The group argued that the agency had flouted numerous procedures when it made the rule change, building its case mostly on procedural law rather than invoking the Second Amendment. In part, the group challenged ATF’s divergence from its previous interpretation of the law, when it concluded in the mid-2000s that only a certain type of bump stock should be banned.

But Friedrich said ATF did not violate any laws under the Administrative Procedure Act as it reconsidered whether a bump stock was a machine gun and declined to issue a preliminary injunction against the ban.

“That this decision marked a reversal of ATF’s previous interpretation [of the meaning of bump stock] is not a basis for invalidating the rule,” Friedrich wrote, “because ATF’s current interpretation is lawful and ATF adequately explained the change in interpretation.”

The ruling puts gun-rights groups on a tight timeline should they appeal the ruling, which they indicated in court filings that they plan to do. ATF’s bump-stock ban is slated to go into effect on March 26. At that point, bump-stock owners will be required to destroy the devices by melting or shattering them or to drop them off at an ATF office.

In its rule change, ATF simply clarified the definitions of words like “automatic” and phrases like “single function of the trigger.” The agency has been debating whether certain types of bump stocks should be banned since at least 2002. It decided that a single type of bump stock was illegal in 2006 before expanding that interpretation to all bump stocks in December.

The gun-rights groups also tried to challenge the validity of the rule on the grounds that then-acting attorney general Matthew Whitaker had been unconstitutionally appointed by Trump. Friedrich found that this argument also lacked any merit.

But while support for banning bump stocks is strong on the left, at least some Democrats opposed the ATF rule change. Sen. Dianne Feinstein, D-Calif., argued that the authority to make such changes should rest with Congress.

Feinstein predicted in commentary for The Washington Post that the ban would end up entangled in litigation, possibly preventing it from taking effect.

“Support for banning bump stocks is widespread, and it’s encouraging to see the Trump administration take action on gun safety,” she wrote. “But let’s not celebrate too quickly. Presidents can rescind regulations just as easily as they create them, and in this case, the bump stock ban will likely be tied up in court for years.”

The lawsuit filed by the Firearms Policy Coalition is not the only one pending against the Trump administration over the bump stock ban. A similar case filed by gun-rights groups in the Western District of Michigan is set for a hearing next month.