Joshua Lott for The New York Times

In a significant legal victory for Navajo campaigners, a federal judge has voided a permit for the expansion of one of two operating mines on the Navajo reservation, calling for a more thorough review of the project’s impact on the environment and on cultural sites.

In a decision issued Friday, Judge John L. Kane of United States District Court for the District of Colorado ordered the federal Office of Surface Mining Reclamation and Enforcement, part of the federal Department of Interior, to reassess the proposed expansion of the Navajo Mine on tribal land in New Mexico.

The agency granted the permit for the expansion of mining by 4,800 acres in 2005 after an environmental assessment found that the proposal would have no significant environmental impact.

Navajo groups have long complained of lax oversight of coal operations, one of the largest sources of revenue for the Navajo Nation government. Judge Kane said the federal agency did not comply with the requirements of the National Environmental Policy Act to fully assess potential environmental, cultural and economic effects, like disturbing burial grounds or having to relocate residents.

The judge also ordered “meaningful public notice,” like radio ads in both English and Navajo, to ensure public participation in decisions on mine permits.

The Navajo Mine, operated by BHP Billiton, feeds the Four Corners Power Plant, also on Navajo land in New Mexico. The federal Environmental Protection Agency deems Four Corners one of the most polluting coal-fired power plants in the nation and recently announced that it planned to require the plant to install $717 million in pollution controls to curb emissions.

Friday’s court decision came in response to a lawsuit filed by two conservation groups, the San Juan Citizens Alliance and Dine Citizens Against Ruining Our Environment. Brad Bartlett, their attorney, said the decision amounted to “a significant rebuke of the federal agency changed with protecting communities, land and water from the harms of Western coal mining.”

“This whole area has been utilized for thousands of years by indigenous people,” said Mr. Bartlett, a lawyer at the nonprofit Energy Minerals Law Center in Durango, Colo. “This is where people have buried kin.”

The decision “sends a very clear signal that it’s time for this agency to do its job,” he added.

Christopher J. Holmes, a spokesman for the federal Office of Surface Mining Reclamation and Enforcement, said the agency’s legal staff was reviewing the decision “and of course, we intend to follow the law.” He said he could not answer for decisions made under the previous administration and that the agency’s current leadership had met with tribal leaders and “we take our duties very seriously.”

Officials from BHP Billiton said in a statement that they were reviewing the judge’s order and had temporarily suspended mining operations in an area covered by the disputed permit.

“At this time, BHP Billiton does not know the specific impacts this decision may have on Navajo Mine,” the statement said.