Your argument would hold water only if meth, cocaine,pot,were legally sold .they aren't.
Current strategy is to keep illegal street prices expensive. This just keeps crime profits lofty, and tempts users to steal. I would prefer that they switch to prioritizing keeping non users safe on the streets.
...in prison,they must attend na,aa for any criminal offense if they are also an addict.
Yes, treatment. That is what I am recommending. AA, NA, Teen Challenge and such are great. Keep up the good work.