Does Congress's power to tax give it the power to punish the possession of unregistered machineguns under § 5861(d) of the NFA, even though it is impossible to register and pay tax on those machineguns, the law generates no revenue, and the only enforcement mechanism is prosecution?

QUESTIONS PRESENTED When the National Firearms Act (“NFA”) was passed in 1934, the sole constitutional authority for the law was Congress’s power to tax under U.S. Const. Article I, § 8, cl. 1. Congress recognized that it did not have the power to ban disfavored firearms outright. So instead, it passed a law that required certain “noxious” firearms, including machineguns, be registered and taxed. See 26 U.S.C. § 5861(d). Fifty-two years later, however, Congress passed the Firearms Owner Protection Act (““FOPA”). Enacted under Congress’s newly expanded Commerce Clause power, the FOPA banned the possession of all previously unregistered machineguns. See 18 U.S.C. § 922(0). Since the passage of § 922(0), the government has steadfastly refused to register or tax the possession of previously unregistered machineguns under the NFA. But, it continues to prosecute and imprison individuals for failing to register those machineguns. Does Congress’s power to tax give it the power to punish the possession of unregistered machineguns under § 5861(d) of the NFA, even though it is impossible to register and pay tax on those machineguns, the law generates no revenue, and the only enforcement mechanism is prosecution? i