The Navajo Nation-based firm has yet to obtain the leases for the mines. Before the government can transfer leases to a new owner, all past-due royalty payments need to be settled. The tax hiccup could become a headache for both the new owner and Wyoming taxpayers alike.

“(The unpaid royalties) could be a block to NTEC getting the leases and officially taking over the mines here in Wyoming,” said Shannon Anderson, an attorney with Powder River Basin Resource Council, a landowners group. “Until they get the leases, they can’t get the permits.”

Cloud Peak Energy still holds the permits for the three mines and is therefore responsible for future cleanup obligations. And NTEC will continue to operate as a temporary contract miner in both Wyoming and Montana until it pays up.

But for Anderson, the unpaid federal taxes could have troubling consequences for Wyoming residents.

“Approximately half of all the royalties from federal minerals developed within the state of Wyoming come back to Wyoming,” she said. “It is just an incredibly important source of revenue for Wyoming, and especially our school system. Every dollar that we don’t get back here in Wyoming is another dollar that doesn’t go to schools.