Like most of our elected wars, the war on drugs is producing more costs than benefits. In the United States, those drugs that were around for the last one to two hundred years have been legal at times and illegal at other times. There was no significant difference in the recorded use of these drugs when they were legal and when they were not (the data has to be rather sketchy, however). So there has been no measurable benefit.
The costs of outlawing drugs, however, have been enormous. The large expenditures on police, armies, courts, jails are nothing compared with the costs to society (on both sides of our Southern border) of creating the large criminal industry that grows, refines, transports, and markets these drugs and the lawlessness that accompanies it. Over the last thirty years 50,000 deaths have been attributed to drug related violence in Mexico alone. The Presidents of Colombia, Guatemala and Mexico are all now calling for a reconsideration of this war as an effective approach to dealing with the harm of some of these drugs.
Another good article in the Washington Post: http://www.washingtonpost.com/opinions/from-latin-america-a-new-strategy-in-the-war-on-drugs/2012/04/12/gIQAowenDT_story.html
Marijuana should be regulated like tobacco and cocaine and opium should be regulated like alcohol. We seem to be moving in the right direction on this issue but too slowly.