In 200 years history of drug suppression literally everything has been tried.
And yet, even in a high security prison, drugs are highly available.
If it can't be done in a max-security prison, how do you think it can work for a whole society?
What method of restricting supply has not been tried. The US has literally invaded other country to try to destroy supply bases. The military as whole division, billions spent on intercepting submarines.
Absurd high cost have been put on a dealer that is captured.
What is your solution to actually restrict supply in a meaningful way?