CHEYENNE, Wyo. (AP) — The U.S. Environmental Protection Agency has determined that nearly 1.5 million acres around Riverton that Congress opened for settlement by non-Indians early last century remains legally Indian Country.

The EPA on Friday sent notice to the Eastern Shoshone and Northern Arapaho Tribes that the federal agency has approved their application to have the Wind River Indian Reservation treated as a separate state for purposes of implementing the federal Clean Air Act.

In setting formal reservation boundaries, the EPA agreed with the tribes that a 1905 federal law that opened reservation lands around Riverton to settlement by non-Indians didn't extinguish the land's reservation status.

Gov. Matt Mead wrote to the EPA in August warning that accepting the tribes' position would have implications for criminal law, civil law, water law and taxation.