Whether the definition of 'machinegun' in 26 U.S.C. §5845(b) includes non-mechanical bump stocks

QUESTIONS PRESENTED The question of statutory construction at the heart of this case concerns the meaning of the term “machinegun,” as defined by Congress in 26 U.S.C. § 5845(b). In 2018, the Bureau of Alcohol, Tobacco, Firearms and Explosives (“ATF”) issued a set of regulations (collectively, “the Rule”), that reinterpreted “machinegun” more expansively than ever before to prohibit, for the first time, accessories known as non-mechanical bump stocks. Nevertheless, the D.C. Circuit upheld the Rule on summary judgment, finding that ATF’s novel interpretation of “machinegun” was, in fact, “the best interpretation.” In doing so, the court of appeals eschewed the district court’s earlier reliance on Chevron to uphold the rule. The questions presented are: (1) Whether the definition of “machinegun” in 26 U.S.C. §5845(b) includes non-mechanical bump stocks. (2) If the definition of “machinegun” in 26 U.S.C. § 5845(b) is ambiguous, whether that ambiguity should be construed against the Government.