US President Donald Trump has banned bump stocks - a gun device which allows semi-automatic weapons to fire like machine guns - after they were used in the Las Vegas shooting.
The ban was signed on Tuesday, and owners will have until late March to turn them in or destroy them.
The ban will be in force 90 days after it is published in the federal register which is expected to happen on Friday.
The attachment became a focal point of the gun control debate when they were used by Stephen Paddock to open fire on a music festival in Nevada in October last year.
It became the worst mass shooting in US history.
The ban comes as Mr Trump met with a school safety panel, set up in the wake of the massacre in Parkland, Florida - which recommended arming teachers and using veterans as guards.
A Las Vegas Police officer stands near yellow police tape on Las Vegas Boulevard near the Mandalay Hotel and the site of a mass shooting which claimed the lives of 59 people in October 2017 | Image: Nick Otto/Zuma Press/PA Images
The US Federal Commission on School Safety panel rejected calls to increase the minimum age to purchase a gun, arguing that most school gunman get their weapons from friends or family.
It suggested arming staff, saying schools in rural districts would particularly benefit.
Bump stock owners will be required to destroy them or turn them in to the US Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF).
The devices are not traceable, so it is impossible for authorities to be completely sure about how many are owned in America.
The bureau estimates between 28,000 and 520,000 have been sold since 2010.
White House Press Secretary Sarah Huckabee Sanders said the move was Mr Trump "once again fulfilling a promise he made to the American people".
The president promised a ban in March saying the device turns "legal weapons into illegal machines".
US President Donald Trump | File photo
In 2010 the ATF ruled bump stocks did not amount to machine guns and could not be regulated unless Congress changed existing firearms laws or passed a new one.
In the aftermath of the Las Vegas shooting, Congress sought to ban bump stocks, but no new legislation was passed.
At least 10 states have sought to introduce their own restrictions since October last year.
Gun Owners of America said it would file a lawsuit against the US Justice Department and the ATF to protect gun owners from "unconstitutional regulation".
The Justice Department pledged to fight any legal challenge.
The National Rifle Association (NRA) called the decision "disappointing" and called for an amnesty for bump stock owners.
In April, Slide Fire Solutions, the largest manufacturer of bump stocks, announced it would stop taking orders and shut down its website. Their remaining stock was being sold by Texan company RW Arms.
