The U.S. Supreme Court on Friday struck down a federal ban on bump stocks, a gun accessory that enables semiautomatic rifles to fire like machine guns and which was used in the deadliest mass shooting in modern U.S. history.

The decision comes six years after former President Donald Trump directed the Bureau of Alcohol, Tobacco, Firearms and Explosives to ban the accessory following a 2017 shooting at a country music festival in Las Vegas. The gunman there fired more than 1,000 rounds into a crowd in 11 minutes, killing 60 and injuring hundreds. A gunman in another shooting, one at a high school in Parkland, Florida, used a rifle with a bump stock to kill 17.

The court voted 6-3 to reverse the Trump-era ban, with the six justices appointed by Republican presidents in the majority. Justice Clarence Thomas wrote the majority opinion, which found that bump stocks do not convert firearms into illegal machine guns because they do not make a weapon fire more than one shot with a single trigger pull.

The National Firearms Act of 1934 defines a machine gun as a weapon that fires automatically more than one shot by a “single function of the trigger.” Bump stocks harness the weapon’s recoil to rock the weapon back and forth in the shooter’s hands, rapidly engaging the trigger. The rate of fire, Thomas wrote, is similar to that of a machine gun.

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“A bump stock merely reduces the amount of time that elapses between separate functions of the trigger,” Thomas wrote.

Justice Sonia Sotomayor wrote the dissent for the liberal wing of the court. In it, she took issue with the conservatives’ view of what a machine gun is.

“When I see a bird that walks like a duck, swims like a duck, and quacks like a duck, I call that bird a duck,” Sotomayor wrote. “A bump-stock-equipped semiautomatic rifle fires ‘automatically more than one shot, without manual reloading, by a single function of the trigger.”

Maryland is one of fifteen states, along with the District of Columbia, that have laws banning bump stocks or other “rapid fire trigger activators.” The Supreme Court’s decision does not impact Maryland’s ban, meaning bump stocks and other rapid fire trigger activators cannot be sold or possessed in the state, according to the Maryland Attorney General’s Office.

Attorney General Anthony Brown, in a statement Friday afternoon, called the decision “a step backwards for common-sense gun laws.”

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“We needlessly lose innocent lives by ignoring the lethality of the weapons and gun accessories that are in our communities,” Brown said. “I will continue fighting to eliminate gun violence and to uphold common-sense gun control.”

A spokesperson for Gov. Wes Moore’s office did not immediately return a request for comment.

Maryland’s law has been challenged before, but the Supreme Court declined to take it up. A lower federal court ruled that the state’s ban on rapid fire trigger activators can remain in place.

Bump stocks are relatively uncommon in Baltimore street crime, but another type of rapid-fire trigger activator is recovered by police with regularity. Known as “Glock switches,” they are tiny accessories inserted into the back of a Glock-style handgun that convert the handgun from semi- to fully automatic. They are known as auto sears, giggle switches or buttons.

Baltimore Police recovered at least 59 in 2023, a review of a list of firearms the department seized last year shows. That’s more than five times as many as the department recovered in 2022, according to a Banner analysis of firearm recovery data.

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This article may update.

The Associated Press contributed reporting.