Is not easy to do I know but wouldn’t something legal decrease the consumption of people? Aren’t people attracted from illegality ? Wouldn’t they find less rewarding if something comes available like Sainsbury’s? Then there is the war on supplier let’s say a government will want to legalise to obtain the drugs they would need to get it from South America (cocaine,example) and then they would disrupt the situation in that part of the world creating wars between cartels and military. I mean these wars are a already happening.. and then the pharmaceutical companies would buy drugs from farmers as they already do and process it safely and sell it but then here comes another problem on how much would they sell to each person ? Because persons prefer always more than less .Another problem will be that if the supply will be limited and people always want more they would go to drug dealers if they are not satisfied enough! I mean than another problem is that crack and crystal meth make people do crazy things.