WASHINGTON — The Supreme Court appeared torn Wednesday over a challenge to a Trump-era ban on bump stocks, a gun accessory that allows semi-automatic weapons to fire rapidly like machine guns and was used in the deadliest mass shooting in modern U.S. history.The high court is weighing whether the Trump administration followed federal law when it reversed course and banned bump stocks after a gunman in Las Vegas attacked a country music festival with assault-style rifles in 2017.Many of the weapons were equipped with …