A newly enforced federal ban on firearm bump stocks will stay in place for the time being, after the Supreme Court again rejected efforts by gun-rights groups to delay its implementation.
The devices allow semi-automatic weapons to fire with greater rapidity, like machine guns.
An order issued Thursday was the second one from the high court. Chief Justice John Roberts turned aside a similar request earlier this week as litigation over the government's new policy continues in federal court.
President Trump signed an order on Feb. 20, 2018, directing the Justice Department to ban "bump stocks" and other gun modifiers that make semi-automatic firearms fire faster. The Trump administration's ban went into effect Tuesday, and follows calls for action after the 2017 massacre in Las Vegas, where 58 people were killed by a gunman who modified his weapons with bump stocks.
The case -- Gun Owners of America, Inc. v. Barr -- puts the Trump administration in an unusual position of arguing against gun-rights groups.
"We must move past clichés and tired debates and focus on evidence-based solutions and security measures that actually work," Trump previously said during a ceremony to honor the 17 victims of the shooting at Marjory Stoneman Douglas High School in Parkland, Florida.
Semi-automatic rifles with bump stocks could fire hundreds of rounds per minute, according to experts. They were originally created to make it easier for people with disabilities to fire a gun.
The device essentially replaces the gun's stock and pistol grip and causes the weapon to buck back and forth, repeatedly "bumping" the trigger against the shooter's finger.
Since the Las Vegas shooting, states and cities increasingly pushed for legislation to ban the devices.
Massachusetts became the first state to pass legislation banning the device after the incident. The state law, which went into effect Feb. 1, 2018, prohibits possession of the device under all circumstances. It also bans the possession of trigger cranks.
The National Rifle Association (NRA) even called for an immediate review of bump stocks after the Vegas shooting.
"The NRA believes that devices designed to allow semi-automatic rifles to function like fully-automatic rifles should be subject to additional regulations," the NRA said in a statement at the time.
Fox News' Jennifer Earl and The Associated Press contributed to this report.