I don't agree that it is the proper role of government to be involved in the regulation of drug use at all, except to the extent necessary to protect life, liberty, and property (which I foresee would be a very minimal role if drug production, trade, and use were legalized).
But I agree with the following comments by "The Economist", "Legalisation would not only drive away the gangsters; it would transform drugs from a law-and-order problem into a public-health problem, which is how they ought to be treated... Most consumers of illegal drugs, including cocaine and even heroin, take them only occasionally. They do so because they derive enjoyment from them (as they do from whisky or a Marlboro Light). It is not the state’s job to stop them from doing so."
How to stop the drug wars | The Economist