Bubbling with euphoria as thick as the haze in the air, marijuana enthusiasts flocked this weekend to Brazil's first "ExpoCannabis," amid a national debate over decriminalizing the drug for personal use.

Launched in Uruguay a decade ago, the huge marijuana fair opened its first international edition Friday in Sao Paulo, complete with DJs, guest speakers, myriad pot products and a large outdoor space packed with hundreds of visitors, nearly all of them smoking up.

Organizers said they expected 20,000 people to attend the three-day event, which aims to showcase cannabis in its many uses, and not just recreational and medicinal.

"We want to show the public all the plant's capabilities. We're not just talking about the pharmaceutical industry. The plant can also work in the food and beverage industry, the construction industry, the textile industry and biofuels," organizer Larissa Uchida told AFP.

"It's a plant that has been demonized for many years, so there needs to be a whole deconstruction of this idea."

Uchida said the event respected Brazilian legislation, with vendors selling cannabis accessories, extracts and derivatives — but not the actual drug.

Those smoking it at the fair likely purchased it illegally, but authorities appeared willing to turn a blind eye.

Brazil's 2006 drug law imposes prison terms for drug trafficking, and lighter penalties such as community service for possession, but has faced criticism for a lack of clarity over the line between the two.

– Landmark court case –

ExpoCannabis got its start in Uruguay in 2013, the same year the small South American country became the first in the world to fully legalize the regulated production and sale of recreational marijuana.

The event in neighboring Brazil comes as the Latin American economic powerhouse re-evaluates its own prohibitionist drug laws.

Brazil's Supreme Court is currently hearing a case that could decriminalize small-scale possession and use of cannabis and certain other drugs in the nation of 203 million people.

Five of the court's 11 justices have so far ruled for decriminalizing marijuana for personal use, just one vote short of the majority needed.

Ruling to decriminalize in August, Justice Alexandre de Moraes condemned existing anti-narcotics laws, which he said principally penalized "young people, especially uneducated Blacks, who are treated as drug traffickers for possessing small quantities."

However, in a sign of how controversial the subject remains, Senate president Rodrigo Pacheco announced plans Thursday to introduce legislation to amend the constitution to explicitly make the possession of any amount of cannabis a crime.

– Budding mega-industry –

"I think it's very important to have the first edition (of ExpoCannabis) in Brazil right now," Sao Paulo state legislator Caio Franca told AFP at the fair.

"We're at a very opportune moment for a conversation on cannabis-based medicines and recreational use, both from a legislative point of view and also in the courts," said Franca, who has introduced a bill to include medical marijuana in the Sao Paulo public health system.

Marijuana for medical use also remains a touchy subject in Brazil. Patients have had to go to court to win the right to use the active ingredient cannabidiol, or CBD, for treatment of conditions such as epilepsy.

Gabriel Vieira, an exhibitor at the fair, called for Brazil to join the growing number of countries that have partially or fully legalized cannabis.

"We have to see the truth: there are a lot of people who consume it, whether it's medicinal or recreational. I think we need to follow in the footsteps of countries like Germany, the United States," said Vieira, who is 29.

The economic potential of the budding global cannabis industry — valued at $43.7 billion last year, and projected to grow to more than 10 times that by 2030 — was on full display at the fair.

Visitor Luciano Narita, 40, grinned as he showed off his haul of products.

"I came here looking for new products, like this chocolate I bought, pipes, leaves," he said with a smile.

"I like it for recreational use."

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© Agence France-Presse