The best option is to make all drugs easily available via proper government facilities and very low prices - this removes the huge profit margins that attracts the criminals, they won't compete with the government at low prices, nothing in it for them - plus it gives the authorities a good idea of what's going on and the chance to start steering people away from usage.
I know, a pipe dream (no pun intended) as there is big money to be made by too many influencial individuals.