A Rio Tinto subsidiary's legal challenge to the cessation of a lease over the Jabiluka uranium mine will have one more opponent after a judge allowed the area's traditional owners to participate.
The mine is under lease to Energy Resources of Australia (ERA) which also operates the adjacent defunct Ranger uranium mine next to Kakadu National Park, near Jabiru, 300km east of Darwin.
ERA had been granted access to the Jabiluka area, an as-yet undeveloped uranium deposit south of Ranger that is estimated to hold 137,100 tonnes of uranium oxide.
About two weeks before the 42-year lease expired in August, the then NT Labor mining minister, Mark Monaghan, refused to extend it after receiving advice from federal Labor Resources Minister Madeleine King.
The lease renewal was rejected partially due to federal government plans to extend Kakadu National Park into the area.
ERA has challenged this decision in the Federal Court.
The firm has sued Ms King, Mr Monaghan, the federal and Northern Territory governments as well as the Jabiluka Aboriginal Land Trust and the Northern Land Council.
After a brief hearing on Monday afternoon, Justice Geoffrey Kennett allowed Yvonne Margarula, representing the Mirarr Traditional Owners of the Jabiluka site, to join the lawsuit in opposition to ERA's claims.
Ms Margarula's barrister Ruth Higgins SC said her client had the right to join in the case as her interests and that of the Mirarr would be affected if the lease was extended.
The lease detracted from the Mirarr people's rights to access and use the land as they saw fit, the court heard.
Furthermore, there was rock art and sacred sites within the Jabiluka area that the traditional owners had a responsibility to look after, Dr Higgins said.
Allowing Ms Margarula and her legal team to contest the lawsuit would ensure all the necessary facts were before the judge and all issues would be dealt with together, she added.
A four-day hearing has been scheduled to begin on October 28.
In a statement, Ms Margarula welcomed the government's decision not to allow the continuation of mining at Jabiluka which her people had opposed for decades.
She expressed a desire to get the younger Mirarr generation there working as rangers to take care of the country.
"Our next generation needs us to teach them. If we wait any longer, who will teach them?" she asked.
"We are the ones that lived on that country, we walked by foot with our mum and dad and our grandmothers right across Jabiluka."
The Jabiluka mineral lease has an estimated value of around $90 million.
An offer to buy the lease for $550 million by Boss Energy was withdrawn after federal Environment Minister Tanya Plibersek said in July the government intended to incorporate the site into Kakadu, ERA said in affidavits filed with the court.
In its 2023 annual report, ERA said there were no plans to develop the Jabiluka area into a uranium mine, saying it could not do so without the approval of the Mirarr traditional owners.
It has said its priority would be to rehabilitate the Ranger mine, which comes at an estimated cost of $2.2 billion.