Testifying in favor of the National Firearms Act (NFA) in 1934, Attorney General Homer S. Cummings noted that the federal government "of course" had "no inherent police powers to go into certain localities and deal with local crime." Rather, "it is only when we can reach those things under the interstate commerce provision, or under the use of the mails, or by the power of taxation, that we can act."
Cummings explained how "the power of taxation" worked in this context: "If we made a statute absolutely forbidding any human being to have a machine gun, you might say there is some constitutional question involved. But when you say, 'We will tax the machine gun,' and when you say that the absence of a license showing payment of the tax has been made indicates that a crime has been perpetrated, you are easily within the law."
