Supreme Court Chief Justice John Roberts has denied an emergency request by gun owners’ groups to temporarily stay the Trump administration’s ban on bump stocks. The ban took effect at midnight Tuesday. One more stay request is reported to be still pending with Justice Sonya Sotomayor. Unless the court intervenes, bump stocks—the devices that enable semi-automatic rifles to fire almost as quickly as machine guns—will be banned nationwide. The devices came under intense scrutiny after a gunman used them during the October 2017 Las Vegas Strip massacre that killed 58 people and wounded hundreds of others. The Justice Department issued the ban on Dec. 26, effectively classifying bump stocks as machine guns “because such devices allow a shooter of a semiautomatic firearm to initiate a continuous firing cycle with a single pull of the trigger.” Bump-stock owners were given 90 days to turn them in or destroy them.