Criminalisation of otherwise law-abiding, tax-paying, functioning members of society is, frankly, stupid.
I think drugs should only be controlled if there is sufficient evidence to suggest that control will actually help users/society. Take Psilocybin mushrooms for example. There appears to be zero evidence (and therefore zero reason) to suggest that this needs to be a controlled substance.
Remove blanket bans on substances which haven't been the subject of scientific/medical research.