Should make it clear I’m not up on the specifics of this case.
My comment was more general in nature.
The issue has been percolating for decades, and there are conflicting state supreme court decisions. In one case on water rights the city was ruled to be on the reservation and in a criminal case the city was ruled to be off the reservation.
These are both state laws/regs and the decision ultimately needs to be resolved by the federal courts, but they had no way of getting it into federal court.
Now, EPA, DOI, and the Justice dept make a decision revolving around air pollution and the Clean Air Act is federal, which allows them to take it into federal court.
The irony is that the Wyoming politicians didn't have any objections with this until the story went national and the right wing media picks it up, and now the politicians have to change their tune, or they might get unelected by a tea partier. Cheney's daughter might run for their office.