Here is the petition in Wilton Rancheria v. UNITE HERE:

Question presented:

Notwithstanding the deference afforded to arbitration awards, arbitrators lack the power to facially invalidate federal and state statutes. Similarly, courts defer to Tribal interpretation of Tribal law, as a critical element of longstanding policies upholding and safeguarding Tribal sovereignty. Does an arbitrator exceed his authority when he facially invalidates a duly-enacted Tribal law, especially when a court would not do so and when he would not be permitted to invalidate a duly-enacted federal or state statute?

Lower court materials here. Ninth Circuit unpublished opinion here.