Mexico announced recently that it will decriminalize the possession of "small amounts of drugs"—marijuana, cocaine, LSD, methamphetamines, heroin and opium—"for personal use." Individuals who are caught by law enforcement with quantities below established thresholds will no longer face criminal prosecution. A person apprehended three times with amounts below the minimum, though, will face mandatory treatment.

For the government of President Felipe Calderón, which has spent the...