From this it would seem that marijuana is an herbal remedy, not a drug, under the law.
"The DSHEA law draws a line between synthesized medicines like aspirin and remedies made from herbs, minerals, vitamins and amino acids. This latter group was recategorized as "dietary supplements" -- that is, as foods rather than drugs."
Link: Herbal remedies need real scrutiny - CNN.com
Does the FDA police any other herbal remedies? Any other herbal toxins for that matter?