Have you heard the story of the residents of Riverton, Wyo.? One day they were Wyomingans, the next they were members of the Wind River tribes — after the Environmental Protection Agency declared the town part of the Wind River Indian Reservation, undoing a 1905 law passed by Congress and angering state officials.

The surprise decision was made by officials of the EPA, the Department of Interior, and Department of Justice early last month, and has invoked the ire of Gov. Matt Mead, who has vowed not to honor the agency’s decision and is preparing to fight in court.

“My deep concern is about an administrative agency of the federal government altering a state’s boundary and going against over 100 years of history and law,” Mead said in a statement. “This should be a concern to all citizens because, if the EPA can unilaterally take land away from a state, where will it stop?”