For everything else, like the "crack and smack" you seem so peculiarly familiar and obsessed with--substances, by the way, that are abused by a smaller percent of the population than there were Harry Browne voters in 2000---could be dispensed by prescription only.
Libertarian doctrine doesn't allow for distinctions to be drawn between crack and pot.
...could be dispensed by prescription only.
By an unlicensed Doctor Feelgood working the sidewalk?
That's the same as saying you're in favor of prohibition, Axe. If a person has to get a doctor's prescription for meth or crack cocaine, he or she will just turn to the black market. No doctor is going to prescribe such dangerous substances to a patient, unless you want to outlaw the Hypocratic Oath in order to legalize irresponsibility.