Numerous countries restrict the import of various things due to their potential for illicit drug use. However, all of these countries recognise the value of controlled use of the same drugs.
This means that;
Afghan farmers grow Poppies that are used both for legal and illegal heroin production.
farmers grow coca plants that are used both for legal and illegal cocaine production.*
Yet international movements of the raw material for these products are heavily (and expensively) controlled - despite the raw constituents being relatively benign in comparison to their processed derivatives.
This heavy control on supply creates artificially high profit margins for those willing to break international law, funding them well enough to exert an incredible amount of power over the farmers who grow the stuff, as well as funding vast and complex organisations dealing with shipment, money laundering, etc.
This in turn creates regions of political instability, where it is profitable (and militarily possible, with suitable funding) to flout common standards of law, order and democracy.
Looking at the problems caused by illicit drugs, we have to include those who suffer at the production end just as much (if not more than) those who suffer at the usage end.
Were we to limit import/export restrictions only to the processed forms of these drugs, we would be able to remove the control of ruthless coca/heroin barons over remote but vast areas of the globe, while still maintaining some control over drug production (both legal and illicit) since all processed forms of these drugs could be performed safely within a country's borders at government licensed facilities.
It would become cost effective for illegal sellers of drugs to open their own back-yard processing facilities in order to produce their own derivatives from raw product, rather than rely on international criminal gangs to continue producing it abroad and smuggling it in over the borders. This again would break down the established international hierarchies of crime, while still allowing national police forces to control any such facilities (as they might do already for methamphetamine, crack labs or whiskey stills).
Essentially, by reducing the profit margins by democratising production (an open-source drugs policy if you will) which in turn should disperse those operating illegal refinement facilities, (once more further reducing potential profit margins) there should** be an overall reduction in drug usage and hence, related crime.
This leads towards a twin strategy, a complete liberalisation on the cultivation and distribution of raw materials (within and across borders) whilst maintaining a strict control over the processed derivatives of those materials.
*The two examples used here are coca, and opium poppies - but I'm sure there must be other examples of this kind of restriction. The point about legal and illegal usage is to suggest that the actual growers themselves are not necessarily evil, breaking the law, or doing anything that might be considered wrong - it's those in control of these farmers, and their product's distribution that this idea seeks to address.
**With low profit margins and access made available to more (still illegal) players in the field, there should to be less coercion for people to get involved in drugs in the first place.