In that span of time, there has been no other nation on the planet with greater technological, military, financial resources to throw at something like prosecuting the so called war on drugs. If the US couldn't kill the cartels & illegal supply with that approach, it can't be done that way. The fact that it would fail was always an obvious logical conclusion ahead of time (we even had prohibition to reference as a blatant demonstration), but we have the benefit of vast actual results of perpetual failure and destruction to throw on top of just reasoning it through.
Fortunately the majority of Americans have come around to understanding the war on drugs has completely failed and for that reason the WoD is over (specifically it's on its last legs).
Can't be done. It's useless to waste a single further breath entertaining that idea.
http://www.therooster.com/blog/kids-love-getting-dizzy-and-l...
Would an individual considering whether to buy/use a drug actually evaluate the involvement of a cartel in their decision? I doubt it.
I suspect demand for drugs is largely independent of their legal status. Legalization would not open the floodgates to reservoirs of potential users previously held back by law.
If there is a demand, someone will find a way to make money off of it.