Today, Mountain States Legal Foundation filed a case against the ATF over its Final Rule regulating the self-manufacture of firearms and inoperable weapon parts. Representing Mike Andren, Jennifer VanDerStok, and Tactical Machining, LLC, we seek to block the implementation and enforcement of a new regulation that redefines the statutorily defined term “firearm.” We argue that the ATF’s rule wrongly defines many inert objects as firearms, imposing severe regulatory burdens that will have a chilling effect on the practice of firearm self-manufacture, and exceeds the rule-making authority of the executive branch.