The ban was imposed by the Trump administration after the 2017 mass shooting in Las Vegas and is being defended by the Biden administration.

Some Supreme Court justices on Wednesday expressed reluctance to strike down a ban on “bump stocks,” a gun accessory that allows semi-automatic rifles to fire more quickly, although the final outcome remains unclear.

The prohibition was imposed by the Trump administration after the Las Vegas mass shooting in 2017 in which Stephen Paddock used bump stock-equipped firearms to open fire on a country music festival, initially killing 58 people.

The Supreme Court in 2019 declined to block the regulation. The already conservative court has tilted further to the right since then, with conservative Justice Amy Coney Barrett, a Trump appointee, replacing liberal Justice Ruth Bader Ginsburg, who died in 2020.

Conservatives now have a 6-3 majority that has backed gun rights in previous cases.