Here is the problem. There is no amendment banning heroin, crack, or what ever it is that you do, but there is that little loop hole the size of Texas called the general welfare clause.
Because of that, the states and Fedgov have the authority to make sure that I don't send out a bunch of product with E. Coli in it. Or sell whole milk (if you want to see something impressive, try to sell whole milk on the open market.) Further more, it has been settled law for over a hundred years. When the government mandated pasteurized milk, there were several challenges, some of which reached the USSC. The laws were upheld.
Now, that isn't to say that a new challenge wouldn't be successful, but that it is not likly to succeed. The general welfare clause of the USConst is the basis for the regulation of food and drugs.
That is why you have to prove that you drug of choice is relatively safe.
At the time that clause was put in the Constitution the germ theory of disease was not known ~ that came later. However, they did understand quite well how mixing chemicals in error, or not according to formula, could give you good gunpowder or bad gunpowder, or even infection ~ even if you didn't know about germs.
Somebody thought a single authority should "control" purity of ingredients and also knew that "weight" and "volume" were very good ways to do that.
Now that we can measure and weigh things down almost to the level of granularity of the Universe, seems to me that if you wanted to put the Controlled Substances on a proactive W&M basis you'd get as much control as you do by starting from the Tax Basis used for much of the last century. (NOTE: at the time the USSC didn't think the federales could control dope, but they could control taxes, which the dope peddlers didn't pay. So, Congress passed a tax on MJ, and the rest is history).
Remember, the theory was you could set a standard on almost anything from a central source ~ to wit, Congress (and the agencies created under laws they pass).
Argument from "nature" must extend beyond the substance into relative granularity and topicality. Oh, yes, they got everything they needed at the Constitutional Convention.
Wrong answer. The “general welfare” clause is NOT a grant of authority DESPITE the best efforts of generations of statist thugs. You know, people (and I use the term loosely) not unlike you.
Nor do I use any substance not prescribed for me by competent medical personnel. Or likely would, even when such are re-legalized. My “drug of choice” is being left alone by government and not have to face the ever increasing probability of having my door kicked in or being otherwise violated in the name of protecting me from myself.