Start at the source. The manufacturers. The growers. Then work down from there. The transporters. By ship, by submarine, by plane, by train, by vehicle, by foot. The wholesalers, major distributors, minor distributors, buyers, doctors, sellers, and pushers.
It has been tried to work from the other end; the users. That doesn't seem to work.
It's like trying to put out the growing burning puddle of gasoline instead of closing the valve from the tank feeding it.
While the solution requires a bit of the former to achieve the latter, without the latter, the fire burns on.
OTOH, it is interesting to see that all those tobacco/asbestos/hernia mesh/hip replacement/etc. lawsuit attorneys have found yet another new source of income.