Ok , lets pretent I agree with you.
Impliment it, how? You got guns?
You mean, drug legalization?
It's simple. You legalize the production and consumption of mood-altering drugs with the US.
I'd use the same model that was used for repeal of Prohibition. Let the states decide how they want to participate: some may want to stick with outright prohibition, while others may want only partial legalization.
In my state, there are still "dry" counties and municipalities in which alcoholic beverages cannot be sold, and others in which it is limited to beer and wine. However, possession is legal throughout the state.
I would expect harsh penalties for selling them to minors -- just like we have for alcohol. I would also expect that current laws prohibiting public intoxication, drunk driving, etc. would be expanded to cover everything else that might cause impairment. If anything, I'd like to see those laws strengthened: if you hurt someone or cause damage while under the influence of a substance you took voluntarily, you'll be treated as if you did it intentionally.
I would also like to see laws that prohibit public assistance (welfare, medical, etc.) for people whose problems can be traced to substance abuse of any kind. I'll make an exception for assisting with treatment to beat a habit. But, if you destroy your liver or whatever, you have to live with the consequences and pay for it yourself, or find someone in the private sector that is willing to help you.
Insurance companies already treat smokers as increased risks. People that abuse mood altering drugs should be treated the same way.
Outside the US, I wouldn't do a thing. Once a stable supply is developed within the US, the problem outside the US will take care of itself: the prices will drop and the minimal profits won't be worth the risk. That's exactly what happened when Prohibition was repealed.