The anti-marihuana law of 1937 was largely the federal government's response to political pressure from enforcement agencies and other alarmed groups who feared the use and spread of marihuana by "Mexicans." Recent evidence also suggests that the Federal Bureau of Narcotics resisted the enforcement burden of the antimarihuana law until mounting pressure on the Treasury Department led to a departmental decision, probably in 1935, to appease this fear, mostly in the Southwest and West, by federal legislation. Previously unpublished documents clarify the role of medical research in the campaign for a federal anti-marihuana law and in the Treasury Department's preparation for congressional hearings.
Musto DF. The Marihuana Tax Act of 1937. Arch Gen Psychiatry. 1972;26(2):101–108. doi:10.1001/archpsyc.1972.01750200005002