AGUA PRIETA, Sonora - A few blocks from the municipal police station, on the morning after a cartel gunfight took four more lives in Sonora, drug dealers cruise the streets of La Zona Roja with cellphones in their hands.

Addicts in a local treatment center say these "carros alegres," or happy cars, bring crack cocaine to consumers with all the speed and reliability of a pizza delivery.

The happy cars are one more sign of Mexico's growing drug-abuse problem and serve as a backdrop to the government's decision in August to decriminalize the possession of small amounts of narcotics. When the measure was adopted, President Felipe Calder�n and Mexico's Congress said they wanted to concentrate law-enforcement efforts on the ruthless cartels that are blamed for an estimated 13,000 deaths since Calder�n declared a war on drugs in December 2006. Calder�n also said decriminalization of personal-use quantities would thwart corrupt Mexican cops who sometimes shake down drug users for bribes.

The measure incited controversy from Mexico City to Washington, D.C. Legalization advocates suggested that America's closest neighbor and ally in the drug war had finally recognized the waste of filling prisons with non-violent addicts who need treatment rather than punishment. Drug-enforcement hard-liners warned that eliminating criminal charges for drug abuse would lead to increased public consumption and addiction, perhaps even spawning narco-tourism by Americans looking to get high legally in Mexico.

That the happy cars still cruise about Agua Prieta suggests that critics and supporters overestimated the law's possible effects, both on drug violence and the scourge of addiction.

The reform seems to have had more impact in the rhetorical war over drug decriminalization than it has on Mexican streets. Rather than claiming victory, legalization advocates say the new law may even make things worse because of the way it's written. Conversely, anti-legalization groups condemn the measure because it appears to legitimize drug abuse.

Beneath the lofty debate, cops, treatment counselors, government officials, researchers and addicts interviewed last month said there have been no discernible changes related to the new law.

Police still arrest and incarcerate drug users. Americans have not flocked to dope parlors south of the border. Mexican narcotics abuse surges unabated, as does the flow of drugs and blood.

At the municipal police station in Agua Prieta, Jose Martin Lopez, commander of an anti-narcotics unit, said the enforcement business remains "exactly the same as it was before."

"Nothing has changed," agreed Alejandro Marin, assistant director of a drug treatment center in Nogales. "If police see somebody using drugs, smoking a joint, they pick 'em up."

Kenn Morris, president of a San Diego market research firm that represents the Tijuana tourism bureau, said there is no sign of Americans visiting the border town to use drugs legally. As for the new law's overall impact, he added: "It was a big yawn."

Treatment centers

While public attention focuses on violence and corruption spawned by drug cartels, more damage is hidden away in a Nogales barrio, behind a locked gate with walls topped by barbed wire.

The treatment center is temporary home to 180 addicts, alcoholics and psychiatric cases. Most express ignorance of Mexico's new measure, and many criticize the idea of decriminalization.

"If the law allows us to have a little bit of drugs, then we as addicts will only carry a little bit and a little bit," says Juan Manuel Rodriguez Arroyo, a heroin junkie for 32 years who now serves as volunteer director of the Nogales shelter. "It's bad symbolically. It says you can use and nothing will happen."

Marin, a recovering user as well as administrator, leads visitors past men cooking supper in a cauldron over a wood fire to a windowless detox unit. Several recent arrivals, wrapped in blankets, squint and groan as sunlight breaches the room's darkness.

Next door, in an assembly hall, about three dozen guys take turns proclaiming that they are addicts. A young man in a Denver Broncos jacket, using heavy street slang, orates about the pain he has brought to his family, the damage he has done to himself.

Along Sonora's northern border zone, this is one among dozens of treatment facilities, a sanctuary for crackheads, tweakers, huffers, junkies and boozers. Some residents were committed by police. Some were brought by family members. A few admitted themselves.

At the treatment center in Agua Prieta, a 13-year-old boy, the only child among 84 adults, says he began sniffing inhalants three years ago, then got hooked on cocaine. This is his third time in rehab.

Another cocaine addict, 22-year-old Arturo Quijar Rodriquez, says his wife forced him into recovery because he was neglecting the family. Rodriguez, a municipal police officer, says he is hoping to be back on day shifts soon, while still spending nights in the treatment center.

During a series of interviews at two Sonoran shelters, the stories of dozens of men seemed to blur into one. All started using drugs with friends, wound up dealing or smuggling, spent time in prison. Now, in rehab, they are unanimous in declaring that they want to stay clean.

"It's just like the same movie over and over with a different actor," says Francisco Cardenas, one of the clients.

Legal controversy

The federal decriminalization law, which took effect Aug. 21, calls for suspects caught with small drug quantities to appear before a prosecutor, who must determine whether the possession was for personal use or trafficking. Mexico's government contends the statute merely codifies what already was a legal reality.

The limits include 5 grams for marijuana (about three to six joints, depending on size) and 500 milligrams of cocaine (roughly five doses, or "lines"). Those found to be users must be released with a referral to health authorities, though it's unclear how many referrals are made or whether they work.

At the same time, the law gives Mexico's state and local police more drug-fighting authority. For instance, the measure empowers them to prosecute street drug dealers, a job previously limited to the federal government. It also calls for a central operations center housing drug-enforcement units at all levels in each state. And it toughens penalties - four to eight years in prison - for anyone caught selling even tiny amounts of narcotics.

Finally, the measure allows one year for Mexico's state and local authorities to adopt corresponding personal-use laws and three years to implement them.

But nearly half a year into the new law, many legalization advocates view Mexico's change more as a setback than a victory.

Ethan Nadelmann, executive director of the Drug Policy Alliance, a coalition that favors decriminalization, said most addicts buy drugs in quantities greater than allowed under the measure, so the law in reality would not even decriminalize most "personal use."

"It's not clear yet whether this is three steps forward or two steps forward and three steps backward," he said.

John Walsh, a senior associate at the Washington Office of Latin America, a non-governmental organization that promotes social and economic justice, predicts that Mexico's law will wind up putting more drug users in prison at greater public expense. Because penalties increase for possessing drugs beyond the allowed amounts, he said, the measure also may worsen police corruption, giving officers greater leverage for extortion.

Those who favor rigid enforcement standards are just as critical of Mexico's new standard but for opposite reasons.

"It's a bad message to kids," said Calvina Fay, executive director of Drug Free America Foundation, noting that there is even grass-roots opposition to legalization south of the border. "This is not what moms and dads and grandmas (in Mexico) want for their children. They recognize that drug use is harmful to families."

Fay warns that any softening of enforcement will create safety hazards on highways and in workplaces. She rejects the idea that allowing personal-use amounts will somehow reduce police bribery scams.

"Decriminalizing drugs isn't going to clean up their corruption," she said. "And I don't think it will make one bit of difference as far as easing up the violence."

The larger debate

Because of such philosophical differences, Mexico's reform has emerged as a talking point in the renewed debate over the war on drugs.

Walsh recently co-wrote a report that says decriminalization is spreading through Latin America: Ecuador, Argentina, Brazil, Columbia and now Mexico all have had recent court decisions or legislation eliminating personal-use narcotics offenses.

Walsh said there is little statistical information so far on the impact of decriminalization in Latin America. But in Portugal, where possession of drugs was decriminalized in 2001, research shows improved government control of product safety and distribution, among other issues, without an increase in narcotics use - and without a surge in recreational-drug tourism from surrounding nations.

In the United States, meanwhile, debate has focused primarily on cannabis: Thirteen states already have adopted so-called medical marijuana laws. (Arizona voters are expected to cast ballots on a proposition this fall.) Fourteen states have reduced pot possession from a crime to the equivalent of a traffic ticket. And in October, the Justice Department announced that it will no longer raid properly registered dispensaries of medical marijuana.

Legalization proponents contend these are signs of a nation and world recognizing that the strategy of arrest and imprisonment of drug users is fundamentally flawed. They argue that legal regulation of narcotics would break cartel monopolies while reducing violence, corruption and prison overcrowding. They also contend that the billions of dollars now spent on enforcement could be shifted to treatment and education.

Walter McKay, Mexico City director for Law Enforcement Agents Against Prohibition, said the war on drugs created a lucrative black market that perpetuates cartels and their mayhem. "This is a bloody, costly war," he said. "It's slowly moving toward anarchy."

But in the Nogales rehab center, 55-year-old Carlos Hernandez said a quarter-century of addiction to cocaine and heroin have convinced him that even tiny amounts of narcotics endanger society.

"Oh, yes, it should be illegal," he said. "It destroys lives."