I don't think the government should regulate any drugs, and that the FDA should be in place to make sure that any drugs, as released by pharmaceutical companies or by some individual selling heroin on the street (say - without a license), have been completely tested in order to determine what the complete gamut of effects will be for taking the drug. Further, that the entire onus of any and all effects is on the drug user once ALL the effects have been determined as the user is the one ultimately responsible for putting said drugs into his or her body.
I don't recall the Constitution giving the government the right to provide nanny services for either me or my 350,000,000 American friends, and as a matter of fact, directly interferes with my Constitutional right to pursue happiness as I see fit, as long as it doesn't interfere with anyone else's right to happiness (which would make it more a civil matter than criminal one).