ANCHORAGE — A federal judge was considering Thursday whether a lawsuit alleging federal regulators were in cahoots with opponents of a proposed Alaska mine can proceed.

U.S. District Judge H. Russel Holland heard arguments in the case filed by Pebble Limited Partnership against the U.S. Environmental Protection Agency, which is seeking to have the case dismissed.

The EPA last year proposed restrictions that would essentially block development of the massive gold-and-copper mine near the headwaters of a premier salmon fishery in southwest Alaska. As part of the litigation, Holland ordered in December that the EPA stop all work related to the process pending a ruling on the merits of the case.

In 2011, the EPA, petitioned by Alaska Native tribes and others to protect Bristol Bay, initiated a review that found that large-scale mining in the Bristol Bay watershed posed significant risks to salmon and Alaska Native cultures that rely on the fish.

The agency later invoked a rarely used process through which it could ultimately restrict or prohibit development of the mine to protect the fishery.

Pebble backers sued over that process but Holland ruled the legal action was premature. A panel of judges from the 9th Circuit Court of Appeals upheld Holland’s decision Thursday.

In the separate lawsuit that Holland heard Thursday, Pebble alleges that the EPA violated a federal law by establishing and working with groups of mine critics that essentially acted as advisory committees in the 2014 decision but failed to comply with requirements involving meeting notices and the providing of transcripts.

Brad Rosenberg, a U.S. Department of Justice lawyer representing the EPA, said the agency never created any of the subcommittees. He acknowledged that mine opponents contacted the EPA in attempts to sway opinion but said the Pebble Partnership also had numerous contacts with the EPA, including three meetings with the EPA administrator and 10 with the regional chief.

“If anything, Pebble had unprecedented access,” he said of the creation of the Bristol Bay Watershed Assessment report that served as the basis for the 2014 decision. “It just disagrees with the science.”

Pebble’s attorney, Roger Yoerges, said the EPA created defacto advisory committees to help find a way to block development of the mine.

“They knew the outcome from 2010 forward and manufactured a way to get there,” he said.

The government maintains Pebble can’t be considered an injured party because it was part of the process.

“What that presupposes is that nothing was going on behind closed doors,” Yoerges said.

“What we know is that plenty was going on behind closed doors.”

Holland said he would issue a written ruling at a later time.

Associated Press writer Becky Bohrer in Juneau contributed to this report.