Advocates have long argued that legalization would put a dent in the black market, allow for safe, regulated consumption, create jobs and cut down on crime.
But rather than counting down the days with glee, they're waging an 11th-hour campaign to change legislation that they say would favor large corporations over small businesses and family-owned farms, while doing little to address the issues at the root of the country's illegal drug trade.
"The truth is we're just a few weeks away from the vote and we don't know what's going to happen," said Julio Salazar, a senior lawyer and legalization advocate with the nonprofit group Mexico United Against Crime. "I'm not sure if the initiative being pushed by Congress actually makes things better. It makes a cannabis market for the rich and continues to use criminal law to perpetuate a drug war that has damaged the poorest people with the least opportunities."
The proposal would allow private companies to cultivate and sell marijuana to the public. But it would limit the number of plants an individual could own to six, and require consumers to register for a government license - a step that advocates say could discourage legal use and leave customers likelier to stay in the illegal market.
It would also require commercial sellers to provide seed-to-sale product tracing, akin to the system used in California, but likely to be far more difficult in rural Mexico.
Ricardo Monreal, the Senate leader of President Andrés Manuel López Obrador's ruling Morena party, has said lawmakers considered a number of international models for legalization. The current proposal borrows elements from Uruguay, Canada and some U.S. states.
Advocates fear the legislation, if approved as written, will cut Mexican-owned businesses out of a lucrative new market while doing little to loosen the grip of organized crime on the drug trade.
"We want a legal framework that can bring some of these players in from the illegal market into a legal one," said Zara Snapp, co-founder of the RIA Institute, a Mexico City-based drug policy research and advocacy group. "The purchase price needs to be low enough to undercut the illegal market for consumers. ... You also have to make sure there are enough entry points for (growers) to move over."
If 30 percent of growers can be drawn into the legal market, she said, "that's 30 percent that are paying taxes and out of the shadows, when before it was zero percent."
Neither Monreal nor the Senate commission that is overseeing the legislation responded to requests for comment. Monreal has told reporters that no bill would perfectly address advocates' demands, but ending prohibition is expected to buoy Mexico's economy and allow small farmers a path out from under the cartels.
"The most important thing for Mexico and its legislators is that they dare to knock down this decades-old taboo," Monreal told Reuters this year. The deadline for a vote is Dec. 15.
Marijuana in Mexico has long been the butt of jokes and stereotypes. Snapp hopes the country can overcome that stigma.
"The first time I went to a cannabis expo, there was this Dutch company selling Mexico sativa seeds, and it was crazy to me that there was no way for that to be our intellectual property," she said. "I hope we can start to see a shift where Mexico can take pride in this."
Hemp was brought to the country by Spanish colonists in the 16th century for use as a building material. By the 20th century, marijuana was banned throughout Mexico and the lucrative product moved underground. Marijuana cultivation, much of it for export to the United States, bankrolled the organized crime that continues today in the form of the diversified drug cartels now fueling historically high homicide rates.
But a decade ago, prohibition began to soften. Lawmakers decriminalized possession of small amounts of the drug in 2009; then-president Felipe Calderon, who militarized the fight against the cartels, said the measure would allow law enforcement to shift focus from individual users to large-scale drug dealers and smugglers.
Court rulings loosened regulations still further, leading to the Supreme Court ruling in 2018 that found that banning cannabis violated Mexicans' constitutional rights.
As specialty strains and gourmet cannabis products began to emerge in U.S. states where they were legal, the flow of trafficking flipped: Marijuana grown in the western United States was being smuggled south across the border to consumers willing to pay a premium, according to the U.S. Drug Enforcement Administration.
Today, a lush marijuana field containing hundreds of plants grows in the shadow of the Mexican Senate. Cultivated and tended to by cannabis activists, the protest garden reeks of reefer. It gives advocates a place to light up just steps from where lawmakers will decide how freely they should be allowed to do so.
Despite the steady march toward legalization, attitudes in Mexico around the drug remain fairly conservative. Polls indicate that as many as 60 percent of Mexicans believe marijuana should remain illegal, a finding that lawmakers are expected to take into account.
"Public opinion is important right now because it impacts how politicians think," Snapp said. "But what the politicians need to remember is that we are not at this point because of public opinion - we are here because the Supreme Court ruled on multiple occasions that any and all Mexicans have the right to the free consumption of cannabis, and inhibiting personal use infringes that right."
Salazar said advocates want a Mexican solution.
"The legislation being pushed took the worst parts of all the different models," Salazar said. "They took the consumer registry from Uruguay that is excessive. They included the traceability requirement from the United States, which makes sense over there because regulation is local, but not in Mexico where it would be federal. And we also copied the lack of reparations to help indigenous communities or those most affected by the war on drugs."
Many of Mexico's farmers, advocates point out, live in rural areas without reliable access to the internet and other technologies that would be required to adhere to some of the proposed regulations, such as tracking the plant from seed to sale.
"The devil is really in the details of these laws," said John Walsh, director of drug policy for the Washington Office on Latin America. "There is no one-size-fits-all legalizing solution.
"With Mexico, is this actually going to be an inclusive market shaped to the country's realities? Or will it be a market controlled by well-heeled, well-financed, well-connected corporations?"