The Trump administration moved Tuesday to officially ban bump stocks, which allow semi-automatic weapons to fire rapidly like automatic firearms, and has made them illegal to possess beginning in late March.
The devices will be banned under a federal law that prohibits machine guns, according to a senior Justice Department official.
Bump stocks became a focal point of the national gun control debate after they were used in October 2017 when a man opened fired from his Las Vegas hotel suite into a crowd at a country music concert below, killing 58 people and injuring hundreds more in the deadliest mass shooting in modern US history.
The regulation, which was signed by Acting Attorney General Matthew Whitaker on Tuesday morning, will go into effect 90 days after it is formally published in the Federal Register, which is expected to happen on Friday, the Justice Department official said.
The official wasn't authorized to discuss the matter publicly ahead of the regulation's formal publication and spoke to the AP on condition of anonymity.
In March, President Donald Trump said his administration would "ban" the devices, which he said "turn legal weapons into illegal machines."