(Bloomberg) -- Panama will strengthen its defense in international arbitration if its contract with First Quantum Minerals Ltd. is declared unconstitutional, according to one of the lawyers leading the fight against the copper miner.

The supreme court is considering a suit from attorney Martita Cornejo which alleges that a deal with the Canadian metals producer this month violated the constitution because there was no competitive public bidding process.

“Without a ruling from the court, we don’t have the best defense at the international level,” Cornejo said Wednesday, in an interview at a street demonstration against the mine in Panama City. “The smartest way the Panamanian authorities can get out of that contract is through a court ruling.”

Environmentalists, labor unions and others have held mass protests since congress on Oct. 20 passed a new contract with First Quantum, giving it the right to produce copper at its site for 20 years, with the option to extend that for a further 20 years. The mine is the company’s flagship asset, and produces about 1.5% of global copper output. 

Cornejo’s challenge to the mine contract was the first the supreme court agreed to consider after President Laurentino Cortizo signed the deal into law last month. The court has since agreed to consider five additional constitutional challenges filed by other lawyers. 

Cornejo said she expects the court to issue a ruling on her suit by the end of this month. 

Cornejo also argues that water contamination from the mine infringes on the “common wellbeing” of Panamanians protected by the constitution, and grants the company excessive rights over national territory. 

It also violates constitutional articles that require the country to follow international treaties it has signed, she said, such as the Escazú Accord which was intended to promote “access to justice in environmental matters”. 

The contract allows the company to lease Panamanian land at an excessively low rate, she said, alleging the mine was allowed to continue operating for two years without a contract after a 2017 supreme court ruling deemed the previous contract unconstitutional. 

Read more: Panama Cut to One Level Above Junk by Moody’s on Fiscal Outlook

The company didn’t immediately reply to a written request for comment. 

Definitive Vote 

The nation’s attorney general Javier Caraballo agreed with Cornejo this week that the contract violates the constitution, and said he would send his opinion to the supreme court. 

On Wednesday night, Panama’s congress voted 63-0 to repeal the revised contract, which would make a proposed referendum superfluous. Congress will convene on Thursday for a definitive vote on the bill. 

However congress votes, Cornejo said a ruling from the supreme court would carry more weight in an eventual international arbitration suit. 

©2023 Bloomberg L.P.