CHEYENNE, Wyo. (AP) – The Northern Arapaho Tribe continues to press its legal claim that tribal members shouldn’t be subject to taxation by the state of Wyoming or Fremont County on privately owned lands around Riverton that lie within the historic boundaries of the Wind River Indian Reservation.

A federal appeals court panel in Denver is set to hear arguments from the Northern Arapaho next week. The tribe is appealing a federal judge’s 2009 ruling that dismissed its legal challenge to the state and county’s taxation authority.

The Arapahos’ claim has implications beyond taxation issues and could affect environmental regulations and the state’s authority to prosecute Native Americans for crimes committed in the area. And whatever the outcome, the case also underscores the difficulties that can arise when separate tribes share a common reservation.

“The tribe’s immunity from state taxation in Indian Country is a critical part of tribal sovereignty,” said Andy Baldwin, attorney for the Northern Arapaho. “The tribe is committed to protecting its sovereignty when the state overreaches.”

U.S. District Judge Clarence Brimmer in Cheyenne ruled in 2009 that the Northern Arapaho Tribe’s lawsuit couldn’t proceed without the involvement of the Eastern Shoshone Tribe and the federal government.

Neither the Shoshone Tribe nor the federal government agreed to participate in the lawsuit. Brimmer ruled that because both have “sovereign immunity,” meaning they generally have to consent to being sued, the Northern Arapaho couldn’t force them to participate in the case.

The Northern Arapaho and the Eastern Shoshone share the Wind River Indian Reservation. Congress in 1905 opened more than 1.4 million acres there to possible settlement by non-Indians

Ultimately about 245,000 acres in the Riverton area went into private ownership, held by both Indians and non-Indians. The Northern Arapaho maintain that although the land went into private hands, it didn’t end the land’s legal status as Indian Country. The state disagrees.

Legal disputes over the status of the private lands, and the status of tribal members on those lands, have persisted for years.

For example, the U.S. Supreme Court last year declined to hear a Northern Arapaho man’s claim that the state of Wyoming lacked authority to prosecute him for murder in his daughter’s death.

Andrew John Yellowbear Jr. is serving a life sentence in state prison in the 2004 beating death of his infant daughter. Both the Wyoming Supreme Court and Brimmer previously rejected his argument that the area of Riverton where the girl was killed was legally still part of the reservation. Yellowbear unsuccessfully argued that he should have been tried in federal court because the state lacked jurisdiction in the case.

The status of the land also is an issue as the tribes seek to take over implementation of federal environmental laws.

The Northern Arapaho claim in their lawsuit that a Wyoming Supreme Court decision on water rights in the 1980s established that the contested area was still legally Indian Country.

If the 10th U.S. Circuit Court of Appeals agrees with the Northern Arapaho, the case still must go back to federal district court for a trial on the taxation question. But, as Brimmer noted in dismissing the suit, the implications of the Northern Arapaho’s case go far beyond whether the state can collect sales tax and car registration fees.

“(T)he 1905 Act area encompasses a vast area of nearly 1.5 million acres, and the state has long assumed jurisdiction over the area,” Brimmer wrote. “To conclude that this area is in fact Indian country would effect a dramatic shift in jurisdiction. A judgment in the absence of the United States undoubtedly would prejudice its jurisdictional interests.”

Martin L. Hardsocg, lawyer with the Wyoming Attorney General’s Office, said he agreed the case’s effects could be far-reaching.

“That’s obviously the concern, is that whatever happens here, the question is whether there’s jurisdiction on any count,” Hardsocg said. “That’s really what hangs in the balance on all of these, is that it could be argued that even though it’s a tax case, it’s a decision that would affect everything else.”

Kimberly Varilek, attorney general of the Eastern Shoshone Tribe, said her office will continue to argue that the Northern Arapaho Tribe’s lawsuit cannot proceed without the Eastern Shoshone’s involvement. She said the Eastern Shoshone declined to waive its sovereign immunity because it didn’t feel it was in the tribe’s best interests to subject itself to federal litigation and be bound by a decision on the boundary question.

“That is the gateway question: Should we be forced to waive our tribal immunity to protect the entire reservation, tribal members on both sides, when the interest of filing federal litigation was primarily started with one tribe?” Varilek said. “That’s a question has yet really to be addressed.”