I agree that the .gov has no business regarding what people put into their bodies. The problem arises when people do stupid things because of the the stuff they are putting into their bodies, affecting the rest of the productive society.
Come visit me in the hospital on any given night to take a look at the stupidity this shit causes first hand.
Come take a look at one of the apartments my parents rent out after the people move out; utterly trashed, usually with drug paraphernalia lying all over the place. And good luck taking them to court to try to get any money out of them because they've blown it all on drugs.
I have yet to hear or see anything good come out of a person who is strung out on heroin. Ever. The shit wrecks their lives, and then when they've run out of money to buy any more, it starts affecting the lives of all the good people they trample on for their next fix.
And you're exactly right about it costing the tax payers as well, what with the DEA, police raids, prison costs, etc. Deregulate everything, tax it, and then give them just enough rope to hang themselves with.
Perhaps I need to revise my criteria a little bit. How about, any person who is on drugs and fucks with the life of another person. If you can be on drugs and affect only yourself, fine, go for it, ruin your life. But if you are on drugs of any kind and start affecting me, or costing me money because of it; you need to go.