The US Supreme Court declined on Tuesday to hear a Native American group's bid based on religious rights to block Rio Tinto and BHP  from gaining control of Arizona land needed to build one of the world's largest copper mines - a project situated on land long used for Apache sacred rituals.

The justices turned away an appeal by Apache Stronghold, an advocacy group comprised of Arizona's San Carlos Apache tribe and conservationists, of a lower court's ruling that allowed the federal government to swap acreage with the mining companies for their Resolution Copper project.

Republican President Donald Trump's administration has sought to move forward with the land transfer and allow the mine's development, but a federal judge in Arizona on May 9 had temporarily blocked it from doing so pending the outcome of the appeal to the Supreme Court.

Conservative Justices Neil Gorsuch and Clarence Thomas dissented, with Gorsuch calling the court's decision a "grave mistake" that would allow the government to destroy the Apaches' sacred site without even at least hearing arguments in their case.

"Just imagine if the government sought to demolish a historic cathedral on so questionable a chain of legal reasoning," Gorsuch said. "I have no doubt that we would find that case worth our time."

The project is 55% owned by British-Australian mining company Rio Tinto and 45% by Australian mining company BHP. Rio Tinto is the project's operator. Both companies have spent more than $2-billion on the project without yet producing any copper.

The plaintiffs sued in 2021 in Arizona federal court to block the project, saying it violated constitutional and statutory protections for religious rights. They argued that the project, because it would destroy a religiously important site, violates the US Constitution's First Amendment protections for the free exercise of religion, as well as a 1993 federal law called the Religious Freedom Restoration Act.

The destruction of the sacred site also would violate a 1852 treaty promising that the U.S. government would protect the land and "secure the permanent prosperity and happiness" of the Native American tribe, the plaintiffs said.

'AN ECONOMIC BOON'

The Supreme Court's action was applauded on Tuesday by Mila Besich, the Democratic mayor of Superior, Arizona, the town closest to the Resolution project.

"We've been waiting on this ruling for a very long time," Besich said. "For Superior and all of Arizona, this project will be an economic boon."

The land swap was approved as part of a defense spending bill signed in 2014 by Democratic President Barack Obama, allowing the companies to exchange acreage they own for a plot of federally owned land about 70 miles (113 km) east of Phoenix known as Oak Flat.

The swap was conditioned on an environmental impact statement for the mine being published by federal regulators, which occurred in January 2021 in the waning days of Trump's first term in office.

The site sits atop a reserve of more than 40-billion pounds (18.1-million metric tons) of copper, a crucial component of electric vehicles and nearly every electronic device.

The land, known as Chi'chil Biłdagoteel in the Apache language, has long been a place where Western Apaches have conduct sacred rituals, according to the Apache group's historian and its lawyers at the Becket Fund for Religious Liberty.

The mine, if it is built, would create a crater 2 miles (3 km) wide and 1,000 feet (304 m) deep that would destroy that worship site. Two other legal challenges to the project are winding their way through courts, one from the San Carlos Apache tribe itself and one from the Center for Biological Diversity, which opposes the mine on environmental grounds.

After a federal judge declined to halt the land transfer in 2021, Apache Stronghold filed an emergency appeal. Shortly before former Democratic President Joe Biden's administration was to respond to that appeal, it announced in March 2021 that it was withdrawing the environmental impact statement, a move that froze the land transfer.

The San Francisco-based 9th US Circuit Court of Appeals in two different rulings declined to block the transfer, mostly recently when a panel of 11 judges ruled 6-5 against the plaintiffs in March 2024. The panel split along ideological lines, with six judges appointed by Republican presidents in the majority.

Judges in the majority throughout the appeals process said that while they were they were sensitive to the religious concerns, they felt compelled to rule narrowly on the question of whether the US government can do what it wants with its own land.

After Trump returned to office, the US Forest Service on April 17 said it would republish within 60 days an environmental report needed for the Resolution Copper project land swap to occur.