If someone is smart enough to safely experiment with clean drugs and be a contributing member to society, let them. If someone is stupid enough to abuse dangerous dirty drugs and kill themselves, that's Darwin at work.
All the laws do is force the idiots to steal and put cash in violent criminal pockets instead of killing themselves quietly and cheaply. The laws do NOTHING to stop people from buying drugs. Right now, I can have any drug I want within a few hours. All I need is enough cash. If I was an addict, I'd have to steal since drugs cost more than gold. If drugs cost pennies, they could waste away until they starve and leave everyone else alone.