At the urging of Mexico, Guatemala and Colombia, world leaders met at the United Nations in a special session last week to discuss saner ways to fight the drug trade. They did not get very far toward a shift in approach. Nonetheless, there was a consensus that investing in health care, addiction treatment and alternatives to incarceration would do more to end the drug trade than relying primarily on prohibition and criminalization.

“A war that has been fought for more than 40 years has not been won,” President Juan Manuel Santos of Colombia said in an interview. “When you do something for 40 years and it doesn’t work, you need to change it.”

Mr. Santos and the presidents of Mexico and Guatemala argue that the war on drugs, which has been largely directed under terms set by the United States, has had devastating effects on their countries, which are hubs of the cocaine, marijuana and heroin trade. “When two elephants fight, the grass always suffers the most,” President Jimmy Morales of Guatemala said, referring to the drug cartels and American law enforcement agencies.

Since 2014, the three governments and like-minded allies have sought to lay the groundwork for changes to the current approach, which is grounded in three international drug accords adopted between the early 1960s and 1988. Those treaties, which required that signatories outlaw the trade and possession of controlled substances — including marijuana — were conceived at a time when international leaders saw law enforcement as the most effective way to curb drug production and consumption.