Mexico’s Congress has just passed legislation that would decriminalize the possession of small quantities of illegal drugs. If President Vicente Fox signs the legislation (and it appears that he will), Mexico will join the ranks of the Netherlands and several other countries that have abandoned the “zero tolerance” model embraced by the United States. Under the new law, possession of up to 25 milligrams of heroin, 5 grams of marijuana (about four joints) or 0.5 grams of cocaine (about 4 “lines”), for personal use would no longer be a criminal offense.

That legislation is a step in the right direction. One of more odious features of the war on drugs is the practice of filling the jails with small-time (often recreational) users. But Mexico’s proposed decriminalization measure does not get to the root of the growing problems of drug-related corruption and violence in that society. As I have documented in my book Bad Neighbor Policy: Washington’s Futile War on Drugs in Latin America and more recently in a Foreign Policy Briefing, Mexico Is Becoming the Next Colombia, most of those problems are caused by the enormous black market premium in the illicit drug trade. Unfortunately, Mexican leaders show no willingness to legalize the manufacture or sale of marijuana, cocaine, and other drugs. Indeed, they have argued that the new law will enable law enforcement agencies to devote more resources to supressing trafficking. That means the huge potential profit in the drug trade will persist—and so will the corruption and violence that is tearing Mexico’s society apart.

The new law is a small step in the right direction. But Mexico (and other countries) need to abandon the entire prohibition model to produce truly meaningful benefits.