I found this extract off a site which is quite interesting,
I'd go one up and decriminalize the growth and wholesaling of cannabis. But narcotics and opium-derived alkaloids are a strict no-no. It has been a long-standing conviction of mine that in an issue of legality, if science can be brought in to simplify the grey areas presented by the combination of ideology and utility, it must be brought in. To be more specific, use/trade of substances that are not toxins according to the medico-legal definition of the word must be decriminalized, and those that are toxins should remain illegal. This immediately makes marijuana/cannabis legal and perhaps LSD too. The alleged reason for the illegal status of cannabis is one of the most believable and best documented conspiracy theory of our times (I tried searching for the article on Wikipedia, unfortunately all references to DuPont's role have been removed from all articles). This causes a new problem - both alcohol and tobacco should be illegal by this definition.
Alcohol has been shown to have various medical benefits when drunk in moderate amounts, including protection against heart disease and protection against renal failure. So it should be retained as legal, but regulated - no alcohol advertisements in electronic media. Tobacco, though, would be illegal in my scheme of things. This is logistically impossible given the current situation. Even a ban on public smoking is supremely difficult to enforce, a blanket ban on tobacco is quite unthinkable. Hence, it should not (can not) be illegalized, but tobacco companies should be taxed until they bleed. I'm sure that the economic benefits derived out of a generation of a lower number of smokers will far outweigh the loss in productivity and revenue resultant from this heavy taxation. Tobacco companies that face losses will have to branch out. (In fact, the continued increase of tax on tobacco products is one of the few heartening things of our budget every year)
So, the final proposal - narcotics and amphetamines illegal, cannabis legal, alcohol legal but unadvertised, tobacco legal but unadvertised and heavily taxed, all others to be judged on similiar grounds after scientific evidence. A most perfect marriage of ideology, science, utility and freedom. What do you say?