Wyoming Gov. Matt Mead (R) is feuding with the EPA over a million acres of land. (Gov. Matt Mead’s office)

Wyoming Gov. Matt Mead (R) said Thursday he will not recognize a determination by the Environmental Protection Agency that more than a million acres of state land still legally belongs to two Native American tribes.

The EPA ruled this month that the land, which includes the city of Riverton, has been a part of the Wind River Indian Reservation for more than a century. The ruling came in response to an application from the Northern Arapaho and Eastern Shoshone tribes, which sought to claim the land to administer the Clean Air Act.

The decision means more federal money for the tribes, and the rights to land that had been opened to non-tribal members under a 1905 act of Congress. It has wide-ranging impacts on criminal law; any member of a tribe who commits a crime on the reservation — which is now a million acres larger — would be prosecuted in tribal courts. And it also impacts the city of Riverton, where businesses will be eligible for new federal tax credits for hiring tribal members.

Wyoming officials, who opposed the tribes’ application, say the law passed more than a century ago means the lands were ceded to the federal government.

In a letter to EPA Administrator Gina McCarthy, Mead said his state wouldn’t recognize the decision. In an interview with the Caspar Star Tribune, Mead said the agency hadn’t given the state proper notice of the decision, and that a court decision was necessary.

“What we have is a regulatory agency with virtually no notice — and in fact we were notified after the fact — that has changed these jurisdictional boundaries, and said, ‘here’s a million acres and the jurisdiction has changed,’ ” Mead told the paper.

Wyoming’s attorney general is preparing an appeal, Mead said. A spokesman for the EPA said the agency was reviewing Mead’s letter.