The administration of U.S. President Joe Biden is in talks with Oklahoma tribes over whether they should have a bigger say over a range of environmental regulations in much of the eastern half of the oil-rich state that was recognized last year as reservation land by the Supreme Court, officials told Reuters.

The discussions have triggered concern within Oklahoma’s Republican government that it risks losing control of a big tax base and has stirred uncertainty over future regulation of natural resources extraction, industry and other development in the region.

The Environmental Protection Agency’s (EPA) Administrator Michael Regan last week had separate calls with Oklahoma Gov. Kevin Stitt and leaders from several tribal nations about the tribes’ desire to have broader oversight on the land recognized by the court, an EPA official said.

“It is a priority of the Biden-Harris administration to respect tribal sovereignty, fulfill federal trust and treaty responsibilities, and engage in robust consultation with tribal nations in policy deliberations that affect tribal communities,” an EPA official told Reuters in a statement.

Days earlier, the Interior Department’s Office of Surface Mining Reclamation and Enforcement notified Oklahoma officials that it would begin discussions with the state and tribes on how to achieve a “responsible and orderly transition” of regulatory responsibility for surface mining in the area.

One Oklahoma official said the move would impact just a handful of mines, but said there is broader concern in the state that this could be a first step toward transferring control over more substantial operations.

The Interior Department declined to comment.

Most of Oklahoma’s oil and gas production is in the western part of the state, but some fields in the eastern part of the state could potentially be affected.

At issue is a July 2020 decision by the Supreme Court recognizing the ongoing existence of the historic Muscogee (Creek) Nation Reservation covering about half the state of Oklahoma, the result of legal wrangling over criminal jurisdiction in a rape case known as McGirt vs. Oklahoma.

After that decision, the Trump administration approved a state request to then-EPA Administrator Andrew Wheeler to retain regulatory jurisdiction over environmental issues on the land, upsetting tribal authorities here who complained they were not consulted.

The governor this week said that he wants to take the case back to the Supreme Court to challenge the 5-4 decision.

“My big fear for the sake of Oklahoma’s future is if it goes into taxation or it bleeds into regulation, then the state of Oklahoma doesn’t have any rights in eastern Oklahoma,” Stitt said on a local news broadcast on Monday night.

Oklahoma Energy Secretary Kenneth Wagner, who participated in a call last week with Regan and Stitt, said the state does not believe the McGirt decision should apply to civil matters.

The tribes, which include the Muscogee (Creek) Nation, along with the Cherokee, Chickasaw, Choctaw and Seminole, meanwhile, are working toward an agreement on shared jurisdiction that they want to present to the federal government.

“The next steps, as we understand it, are for the current EPA administration to report findings of their review of this issue and potentially advise tribes on ways to find a resolution to our concern,” said Tye Baker, senior director of Environmental Protection Services for the Choctaw nation.