I would like to stress the moral wrong of iligalizing any drug. I belive people as moral agents, ends in themselves (ya i read a little to much Kant, use him in every moral post) are not subject to the ends of other people not society unless we chose to make those ends our ends. By illigalizing drugs society is using individuals agains thair will to acheive its own ends of a drug free productie society (personaly i dont think iligalizing drugs has anu positive effect on society but my argument stands even if it did). However if a user is not hurting anyone elses with their drug use the state has no moral authority to prevent them from harming themselves if they wish. Acording to cant the only moral wrong is using people as meean to your own( or societys), ends and that is exactly what this is.
I can go deeper into Kant's moral theory but i hope this is suficient to prove my point.