Once again, gun bans and marijuana prohibiton are found bound together. The law banning the posession of a machine gun without having a virtually unobtainable tax stamp was the model for the Marijuana Tax Act back in the '30's.
Actually you've got that backwards. The "Firearms" "tax" was modeled directly and explicitly on the Harrison Narcotics Act.
"[W]e have followed the Harrison Anti-Narcotic Act in language so as to get the benefit of any possible interpretation that the courts may have made of that act." National Firearms Act: Hearings on H.R. 9066 before the House Comm. on Ways and Means, 73d Cong., 2d Sess. 6 (1934) (testimony of Attorney General Homer Cummings)