What I find amusing is the answers given when you ask the question by what authority does the federal government regulate drugs? Especially given that in order to regulate a particular substance [alcohol] a constitutional amendment was required, which has since been repealed, and no similar amendment exists for drugs.
If I'm feeling particularly clever I'll also show how the War on Drugs is Treason as defined by the Constitution... which, oddly, they never seem to have any counterargument to either.
Even worse, if you actually start looking really closely at the judicial history of the vast majorty of drug laws, the decisions and citations ultimately trace back to prohibition-era court rulings. Interstingly, when the constitution was amended, this edifice of precedent was never similarly stricken. The entire regime of the unconstitutional and immoral "war on drugs" rests on a flimsy house of cards that the government will protect by any means at its disposal, because it is critical to the support of its usurped power.