Many - I'd bet most - pot smokers would be delighted to quietly and legally buy pot at a licensed store and smoke it at home. So let them.
Here is an artist's depiction of "ConservingFreedom" below.
OK, that was funny.
It doesn't stay in their homes, it keeps getting spread to the next generation.
Break the chain of contact, and we can start producing generations free of the attraction to use drugs.