Traditional Owners from the Northern Territory and conservationists who recently lost their legal challenge against a decision to reduce the $520million security bond on the McArthur River mine fear it could set a precedent for government conditions on big-polluting projects.

They have called for urgent reform of mining and environment laws after the Environment Centre NT, Gudanji woman Josephine Davey Green and her husband, Garawa Elder Jack Green, asked the NT Supreme Court for a judicial review of three decisions regarding the lead and zinc mine, about 1,000km southeast of Darwin in the Gulf of Carpentaria.

They argued mining minister Nicole Manison erred in 2020 when she slashed the environmental security bond of the mine by almost $120 million and also approved an expansion of the Glencore-owned mine without a long-term plan for its 2037 closure.

Justice Judith Kelly disagreed and said in her judgement the "plaintiffs have failed to establish that the decisions of the minister which have been challenged in this proceeding have not been made in accordance with the mandatory requirements in the Act or that the decisions are unreasonable".

Mr Green said they were disappointed with the decision and­­ did not have faith in the company's conservation efforts in an area with significant First Nations cultural heritage.

"We need the bond to be bigger to protect the river and our country if something goes wrong," he said.

"Today's decision will not stop us."

Ms Green, a Native Title holder of the McArthur River Mine site, said the government decision could affect her people for thousands of years.

The mine shifted its operations from underground to open cut pit mining in 2006, on the condition of independent environmental monitoring for the life of the mine.

The site has had significant environmental problems since, including high levels of lead in fish nearby, spontaneously combusting waste rock in 2013, a seeping tailings dam, and expansion near cultural and sacred sites.

Environment Centre NT director Kirsty Howey said the court decision showed urgent reform was needed of the territory's environment and mining laws.

"This is a failure of mining regulation, and a disaster for anyone who lives in an area affected by mining," she said.

Environmental Defender's Office managing lawyer Elanor Fenge said the case concerned more than just the people of Borroloola, with EDO chief executive David Morris saying it was about ensuring a toxic legacy was not left by projects without long-term closure plans.

"This is perhaps the worst case of a local community having to live with the government's failures, long after the companies and government decision-makers have moved on," he said.

Ms Manison's office was contacted for comment while Glencore said in a statement the company would "continue to comply with all our legal and regulatory obligations".