Well, congress can pass a law (as long as it's constitutional)! The law that governs mushrooms is the Controlled Substances Act: https://en.wikipedia.org/wiki/

Well, congress can pass a law (as long as it's constitutional)! The law that governs mushrooms is the Controlled Substances Act: https://en.wikipedia.org/wiki/Controlled_Substances_Act https://en.wikipedia.org/wiki/Controlled_Substances_Act This handles all sorts of controlled substances, like prescriptions, as well as illegal substances. Now how does the federal government have control over this? It's probably related to how the FDA (Food and Drug Administration, who determine the different schedules of the substances) got started: https://en.wikipedia.org/wiki/Pure_Food_and_Drug_Act https://en.wikipedia.org/wiki/Pure_Food_and_Drug_Act And that is under the interstate commerce clause of the constitution: https://en.wikipedia.org/wiki/Commerce_Clause https://en.wikipedia.org/wiki/Commerce_Clause Also, since there are multiple international treaties involving drug control, that also puts it in the federal government's purview to regulate.