Gun rights groups are ready to fight Trump's ban on the accessory that fueled the Las Vegas massacre

The gun accessory that enabled the Las Vegas shooter to kill and injure hundreds of concertgoers in such a short time is being banned in the U.S., and gun rights groups are gearing up to fight it.

The Trump administration on Tuesday announced a new regulation banning the sale or possession of bump stocks, which attach to semi-automatic assault rifles and enable them to unleash a hail of machine gun-like fire.

There’s an estimated 520,000 bump stocks in circulation in the U.S. currently, and owners will have 90 days to either destroy them or turn them in to the Bureau of Alcohol, Tobacco, Firearms and Explosives, starting from whenever the regulation is published in the Federal Register, possibly as early as Friday.

Depending on the gun, bump stocks, when attached to semi-automatic rifles, can facilitate firing rates of anywhere between 400 to 800 rounds a minute. Once a relatively obscure device, bump stocks became the object of public scrutiny after the Las Vegas shooter used them in his attack on a country music festival in October 2017, causing about 58 deaths and hundreds of injuries within about 10 minutes.

Investigators discovered 12 bump stocks in the shooter’s hotel room, where he conducted his attack from. The shooting generated a bipartisan interest in banning the devices: at least seven states passed laws banning them in the year following the shooting. In February, President Donald Trump caught the ATF off-guard by calling for a ban.

The Justice Department said Tuesday that the ATF would post instructions for destroying bump stocks on its website.

“We are faithfully following President Trump’s leadership by making clear that bump stocks, which turn semiautomatics into machine guns, are illegal,” acting Attorney General Matthew Whitaker said in a statement, “and we will continue to take illegal guns off of our streets.”

Gun rights groups are already preparing to take legal action. On Tuesday afternoon, Gun Owners of America, a group with over 1.5 million members, announced plans to file suit against the DOJ and the ATF over the ban.

“This case has important implications for gun owners,” said Erich Pratt, the group’s executive director, in a statement. “In the coming days, an estimated half a million bump stock owners will have the difficult decision of either destroying or surrendering their valuable property -- or else risk felony prosecution.”