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In 2009, Mexico passed a law that decriminalized the possession of small amounts of marijuana, cocaine and heroin, and the leftist Democratic Revolution Party has proposed several initiatives to decriminalize cannabis. But Mexican President Enrique Peña Nieto has stated numerous times that he opposes legalization, and thinks it would open the door to increased drug use.



His conservative views are reflected in much of Mexico.



"There are much more serious problems to solve in the country. I can't believe that the Supreme Court is considering this issue which stalks our youth with the threat of addiction," said Consuelo Mendoza, president of the National Assn. for Parents, who was campaigning against decriminalization outside the Supreme Court on Wednesday. "One of the big problems we have is the huge amount of young people who don't have access to education or jobs, but now they are going to have free access to take marijuana. This is terrible."



Pro-legalization campaigners outside the court, meanwhile, lighted joints in celebration.



Mexico City Mayor Miguel Angel Mancera has said that he thinks Mexico City is ready for medical use of cannabis but that it was senseless to talk about such a move without first discussing the commercial issues it would involve.



Advocates argue that removing prohibitions will be a key tool in combating drug violence, which has claimed tens of thousands of lives in Mexico in the last decade as drug gangs fight one another for control of lucrative smuggling routes and challenge a government crackdown.



"We want to create a situation where people who use marijuana don't have to get it from organized crime," said Sanchez.



Alejandro Hope, a security analyst in Mexico City, applauded the "symbolic" decision Wednesday as a move in the right direction. But he said that its early legal and practical effect would be minimal and that expectations should be kept low.



"It won't strike down any laws, it will only protect the plaintiffs," he said.



Health Secretary Mercedes Juan Lopez echoed his remarks.



"From our point of view, this definitely doesn't mean the legalization of marijuana," she said in a television interview. "This is just one amparo granted to four people for their own consumption."



"As the federal government, it's up to us to watch over the people's health," she added, "and we're conscious that marijuana is a substance that can generate addiction, especially in the young, as well as damage to people's health. The most important thing is to reinforce our prevention measures."



Marijuana is the most widely consumed illegal substance in Mexico, and Sanchez said that nearly 60% of prisoners in Mexican federal jails were convicted of offenses related to it. She argues that decriminalization would allow Mexico's police and army to focus on crimes seen as more serious.



But Hope predicted that the Supreme Court ruling and similar cases that may follow would have "almost no effect" on bringing down drug-related violence.



"My guess is that most drug-related homicides aren't connected in any shape or form to marijuana," he said.



Although some analysts estimate that marijuana accounts for about a third of the business of Mexican drug cartels, criminal organizations have been focusing increasingly on heroin and methamphetamine in response to growing demand for those drugs in the United States.



Hope also predicted that few people would bother to grow their own marijuana, should personal cultivation become more widely legal. That would mean that the bulk of the market would remain in the hands of illegal commercial growers.



Some details about the ruling remained unclear, including how much marijuana the four plaintiffs will be allowed to produce and whether they will be free to give it to other users.



Jorge Pardo Rebolledo, who was the only judge to vote against the plaintiffs, expressed concern about where recreational users would get their marijuana — and suggested that they might have to commit a criminal offense to obtain it.



However, Justice Olga Sanchez, who voted in favor of the amparo, said: "Absolute prohibition is excessive.... The right to consumption for recreational means should be authorized in respect for people's personal liberties."



Bonello is a special correspondent. Cecilia Sanchez in The Times' Mexico City bureau contributed to this report.