Or maybe you could move the other way: treat addiction as a disease and provide free, pharmaceutical grade product or methadone substitutes to all that request it, if they suffer from addiction. It costs essentially nothing.
This will not only kill the bulk of market and force dealers out in the open to find new, high risk recreational customers as opposed to cash cow addicts; but will also give a livable life to the addicts by preventing the financial and personal ruin brought by addiction to a substance that is made artificially scarce and expensive.
Most of the problems with addiction stem from this scarcity, not addiction itself: addicts take up a criminal activities to finance their consumption, lose all property and social capital, the product has high variability in potency and adulterants and is very risky to consume, they have to deal with criminals on a daily basis to get it etc.