Once the new regulations are published by the government on Friday, owners of the devices will have 90 days to destroy them or turn them into the Bureau of Alcohol, Tobacco, Firearms and Explosives.

After the Las Vegas shooting, in which 58 people were killed by a gunman who used rifles with bump stocks to fire down on a crowded outdoor music concert, gun-control advocates began pushing for ATF to reexamine regulations so it could declare bump stocks illegal.

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Justice Department officials said they will publish in the public register in coming days their finding that bump-stock-type weapons are machine guns, “because such devices allow a shooter of a semiautomatic firearm to initiate a continuous firing cycle with a single pull of the trigger.”

The move, which had been expected, led three gun rights groups and a bump-stock owner to quickly announce they were suing the government to stop the new regulation.

Joshua Prince, a lawyer representing the plaintiffs, accused ATF of misleading the public about bump stocks. “They are actively attempting to make felons out of people who relied on their legal opinions to lawfully acquire and possess devices the government unilaterally, unconstitutionally, and improperly decided to reclassify as ‘machineguns,’ ” Prince said in a statement.

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RW Arms, a company that sells bump stocks, did not respond to messages seeking comment, nor did the National Rifle Association. The gun rights group has previously urged the government to interpret regulations to restrict bump stocks, rather than seeking a law to ban them.

In 2010, ATF decided it could not regulate bump stocks; officials said the devices did not meet the definition of a machine gun, because they did not permanently alter a gun’s trigger mechanism.

The Trump administration began reexamining its regulations on bump stocks after the Las Vegas shooting, but that effort got a renewed push in April after a mass shooting at Marjory Stoneman Douglas High School in Parkland, Fla., though that attack did not involve bump stock weapons.

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The bump-stock announcement came the same day the Trump administration released a report on school safety from a commission formed after 17 students and teachers were killed in the Parkland shooting. The commission’s report advised against imposing age restrictions for purchasing firearms and suggested that states adopt laws aimed at keeping guns from “individuals who pose a threat to themselves or others.”

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The Las Vegas attack stands as the deadliest mass shooting in modern U.S. history, but it is the only major attack in which the gunman used a bump stock. Law enforcement officials have worried since Las Vegas that its use in that attack could spawn copycat killers.

A 1986 law bans the sale of machine guns manufactured after that year and restricts the sale of such guns made before that year. Because bump stocks were created after 1986, the regulatory change amounts to an effective ban on the devices. Law enforcement agencies are unlikely to use bump-stock weapons, because they are difficult to fire accurately.