Here is the opinion. An excerpt:

This appeal presents the question of whether the grant of federal question jurisdiction in 28 U.S.C. § 1331 encompasses an action to recognize and enforce a tribal court’s award against nonmembers of the tribe. The district court concluded that the action, filed by an Indian tribe seeking to enforce a tribal court judgment against nonmembers, did not present a federal question and dismissed it based on a lack of subject matter jurisdiction. Inherent in the recognition of a tribal court’s judgment against a nonmember is a question regarding the extent of the powers reserved to the tribe under federal law. As in previous decisions involving the application of tribal law to nonmembers, we hold that actions seeking to enforce a tribal judgment against nonmembers raise a substantial question of federal law. We accordingly reverse the district court’s order dismissing the case for lack of subject of matter jurisdiction.

Briefs and lower court materials here.

Here:

Opening brief

Appellee brief

Lower court materials here.