Uruguayans will be allowed to buy enough marijuana to roll about 20 joints a week at a price well below the black market rate, the government said on Tuesday as it detailed a new law legalizing the cannabis trade.

Congress in December approved a law allowing the cultivation and sale of marijuana, making Uruguay the first country to do so, with the aim of wresting the business from criminals.

Leftist President Jose Mujica signed a decree outlining the fine print of the new policy on Tuesday. It says Uruguayans will be able to buy up to 10 grams of marijuana a week at between $0.85 and $1 dollar a gram, a low price designed to compete with black market cannabis that mostly comes from Paraguay.

Activists who have backed the measure said legalized marijuana would be high-grade and affordable.

“You can’t compare a flower that is quality-controlled by the Public Health Ministry ... with Paraguayan (stuff) which is absolutely harmful because it has external substances,” said Bruno Calleros of the Cannabis Liberation Movement.

He said legal marijuana would cost roughly 20 percent of the current market price for similar high-quality marijuana.

Each Uruguayan will also be allowed to grow up to six marijuana plants or the equivalent of 480 grams (about 17 ounces) for personal use and form smoking clubs of 15 to 45 members that can grow up to 99 plants per year.

A sleepy agricultural country of 3.3 million people, Uruguay has come under the spotlight for the marijuana law championed by Mujica, a 78-year-old former Marxist guerrilla whose modest lifestyle and philosophical musings have made him a leftist darling abroad.

Uruguay has gone further than countries that have decriminalized possession or, like the Netherlands, tolerate the sale of marijuana in “coffee shops”. The U.S. states of Washington and Colorado have legalized the sale of cannabis under license, but federal laws still prohibit it.

Uruguay’s experiment is being keenly watched by Latin American peers at a time when the U.S.-led war on drugs faces mounting criticism. Success in Uruguay could fuel momentum for legalization elsewhere.

While relatively prosperous Uruguay has low crime rates, a third of prisoners are behind bars on drug charges.

Advocates of legalization argue that criminalization fuels violence and corruption in developing countries where the drugs are produced or transported. But critics warn that Uruguay’s law could pave the way for harder drugs and lure addicts to Montevideo.

In a bid to avoid becoming a drug hot spot, Uruguay will only allow marijuana to be available to Uruguayan residents who are registered in a confidential database. Still, Mujica has said the country could backpedal if the law fails to work out as planned.

“We’re looking to hurt drug trafficking by snatching part of its market,” Mujica said on Friday, stressing that the law does not seek to foment drug use. “No addiction is good ... The only one I recommend to young people is love.”

Marijuana legalization underlines a profound shift in social policies in Uruguay, which was ruled by a military dictatorship from 1973 to 1985. It has since become one of Latin America’s most liberal countries and has also legalized gay marriage and abortion.

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By Malena Castaldi