After the Bureau of Alcohol, Tobacco, Firearms and Explosives classified bump-stock-equipped rifles as machineguns, a gun owner challenged the rule. The Supreme Court held that a semiautomatic rifle fitted with a bump stock is not a machinegun under the statutory definition. The rifle does not fire more than one shot by a single function of the trigger; the trigger resets and must be reengaged for each shot, even though the device enables rapid fire through continuous forward pressure. The agency could not expand the criminal statute beyond its text. The Fifth Circuit’s judgment setting aside the rule was affirmed.