Isn’t that the case with cigarettes at the minute though?
When’s the last time someone got mugged for cash for cigarettes? Plus the penalties for importing / dealing cigarettes aren’t that severe compared to heroin, so the risk is worth it. Keep the current laws for unauthorised dealing/importing of Class A’s, but this would largely be irrelevant – if you’re a junky do you
A) Steal stuff all day, to get £300 and risk being beaten up/arrested to buy an inferior unsafe product cut with random powder
B) Pay £20 at a government clinic for a pure safe hit
The bottom would fall out of the illegal trade in no time, so the reward wouldn’t be there for the dealers, to make the risk worthwhile.
With cigarettes the risk is still worthwhile.
Edit: I should add, cigarettes are a lot easier to deal, as there are far more addicts, it’s easy to purchase abroad in large quantities, the punishment isn’t that severe, and the product is fairly socially acceptable (than say heroin) so there is no social stigma.