(I apologize if this multiposts; the servers are being erratic.)
There is no justification, though.
The War On Some Drugs is a revenue suck and increases the crime rate – a revenue suck not only because of the enforcement expenses and the cost of keeping criminals in jail on mandatory drug charges, but because regulation and taxation of such things would be a revenue source in a different world – and increases the crime rate not only because peaceable users and carriers are rendered criminal by these statutes, but because there will be demand, and where there is demand there will be supply, and under the current system of laws, most of the people who are willing to provide that supply are criminals.
Never mind that in the absence of regulation, a lot of street drugs are cut with substances that let the dealers sell more of them through dilution, and those substances are often directly harmful to the users, leading to collateral damage through poisoning and other such things that stresses the medical system. Never mind that the pricing on black market drugs can be exorbitant, meaning that more people need to get more money for their fix, money that’s drained out of the legitimate economy and sometimes gotten by theft.
Never mind that the medical uses of various “controlled substances” are being avoided in research and fought in the law-rooms, because these things having an actual beneficial usage would call into question the black-and-white “drugs bad” attitude. Never mind the destructiveness it inflicts on religious traditions that use substances they consider sacred, but which are considered illegal.
Never mind that the DARE program lies to children about the effects of various substances, and several well-informed parents have had to give their children more information about the drugs in question than they wanted to do, in order to debunk the false rhetoric. Never mind that once people catch on that the propaganda is false, they’re entirely likely to stop paying much attention even to the true parts, as they know all about the Government That Cried Wolf. Never mind that prohibition makes drugs, like sex, an act of thoughtless rebellion among people looking for something forbidden to do, and may well discourage them from seeking out and evaluating information.
And never mind that, in all of its inconsistencies and the like, the government has no more legitimate interest in what’s growing in its citizens’ gardens than what’s going on in its citizens’ bedrooms. There are laws against doing harm; there are special cases for those who do harm under the influence of chemistry. That and good information that lets people make sane, reasonable choices about what they do and do not want to partake of strike me as being sufficient and correct.
Prohibition didn’t work when it was alcohol. Why should anyone believe it would work for other things?