Here is the opinion. An excerpt:
Based upon the record evidence, the district court in this matter has done just that–accurately discerned the contemporaneous intent and understanding of the 1882 Act. The court carefully reviewed the relevant legislative history, contemporary historical context, subsequent congressional and administrative references to the reservation, and demographic trends, and did so in such a fashion that any additional analysis would only be unnecessary surplus. Ever mindful to “resolve any ambiguities in favor of the Indians,” there is nothing in this case to overcome the “presumption in favor of the continued existence” of the Omaha Indian Reservation. Yankton Sioux Tribe, 522 U.S. at 344 (quotation omitted); Yankton Sioux Tribe v. Podhradsky, 606 F.3d 985, 991 (8th Cir. 2010) (quotation omitted).
Lower court materials here.