Whether a bump stock device is a 'machinegun' as defined in 26 U.S.C. 5845(b)

QUESTION PRESENTED Since 1986, Congress has prohibited the transfer or possession of any new “machinegun.” 18 U.S.C. 922(0)(1). The National Firearms Act, 26 U.S.C. 5801 et seqg., defines a “machinegun” as “any weapon which shoots, is designed to shoot, or can be readily restored to shoot, automatically more than one shot, without manual reloading, by a single function of the trigger.” 26 U.S.C. 5845(b). The statutory definition also encompasses “any part designed and intended solely and exclusively, or combination of parts designed and intended, for use in converting a weapon into a machinegun.” Ibid. A “bump stock” is a device designed and intended to permit users to convert a semiautomatic rifle so that the rifle can be fired continuously with a single pull of the trigger, discharging potentially hundreds of bullets per minute. In 2018, after a mass shooting in Las Vegas carried out using bump stocks, the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) published an interpretive rule concluding that bump stocks are machineguns as defined in Section 5845(b). In the decision below, the en banc Fifth Circuit held that the ATF rule was unlawful because the statutory definition of “machinegun” does not encompass bump stocks. The question presented is as follows: Whether a bump stock device is a “machinegun” as defined in 26 U.S.C. 5845(b) because it is designed and intended for use in converting a rifle into a machinegun, i.e., into a weapon that fires “automatically more than one shot * * * by a single function of the trigger.” (I)