19 Dec '18 15:20>
The Trump administration has banned the use of bump stocks, devices that let rifles fire like machine guns, after promising to do so earlier this year.
The push to ban bump stocks followed the deadly mass shootings in Las Vegas in October 2017 and Parkland, Florida in February.
Acting Attorney General Matthew Whitaker signed the new regulation on Tuesday, and it is expected to be published in the Federal Register on Friday.
Bump stocks, or slide fire adapters, allow semi-automatic rifles to fire at a high rate, similar to a machine gun, but can be obtained without the extensive background checks required of purchasing automatic weapons.
Las Vegas gunman Stephen Paddock used a bump stock to fire rapidly into the crowd, killing 58 last year.
Following the Las Vegas shooting, lawmakers began discussing a ban on the devices. Shortly after, President Donald Trump directed the Department of Justice to look into changing regulations so that bump stocks would be classified as machine guns, which are illegal to possess in most cases.
The Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) had previously ruled that bump stocks did not qualify as machine guns and thus would not be regulated.
What do gun advocate groups say?
Pro-gun advocates have said they are prepared to fight the rule in court.
The Gun Owners of America lobby issued a statement on Tuesday saying they have prepared a lawsuit against the ATF and the justice department on behalf of the "half a million bump stock owners" forced to part with their "valuable property".
"Agencies are not free to rewrite laws under the guise of 'interpretation' of a statute, especially where the law's meaning is clear," said Erich Pratt, executive director of Gun Owners of America.
The National Rifle Association (NRA), which had called for a review of bump stock devices after the Las Vegas shooting, said they were "disappointed" with the new ban, according to the Associated Press .
An NRA spokeswoman said the government should offer amnesty to current owners.