Justice Gorsuch's conclusion:
The federal government promised the Creek a reservation in perpetuity. Over time, Congress has diminished that reservation. It has sometimes restricted and other times expanded the Tribe’s authority. But Congress has never withdrawn the promised reservation. As a result, many of the arguments before us today follow a sadly familiar pattern. Yes, promises were made, but the price of keeping them has become too great, so now we should just cast a blind eye. We reject that thinking. If Congress wishes towithdraw its promises, it must say so. Unlawful acts, performed long enough and with sufficient vigor, are never enough to amend the law. To hold otherwise would be to elevate the most brazen and longstanding injustices over the law, both rewarding wrong and failing those in the right.The judgment of the Court of Criminal Appeals of Oklahoma isAnd Chief Justice Roberts' dissent intro:
In 1997, the State of Oklahoma convicted petitioner Jimcy McGirt of molesting, raping, and forcibly sodomizing a four-year-old girl, his wife’s granddaughter. McGirt was sentenced to 1,000 years plus life in prison. Today, the Court holds that Oklahoma lacked jurisdiction to prosecute McGirt — on the improbable ground that, unbeknownst to anyone for the past century, a huge swathe of Oklahoma is actually a Creek Indian reservation, on which the State may not prosecute serious crimes committed by Indians like McGirt. Not only does the Court discover a Creek reservation that spans three million acres and includes most of the city of Tulsa, but the Court’s reasoning portends that there are four more such reservations in Oklahoma. The rediscovered reservations encompass the entire eastern half of the State — 19 million acres that are home to 1.8 million people, only 10%–15% of whom are Indians.
Across this vast area, the State’s ability to prosecute serious crimes will be hobbled and decades of past convictions could well be thrown out. On top of that, the Court has profoundly destabilized the governance of eastern Oklahoma. The decision today creates significant uncertainty for the State’s continuing authority over any area that touches Indian affairs, ranging from zoning and taxation to family and environmental law.
None of this is warranted. What has gone unquestioned for a century remains true today: A huge portion of Oklahoma is not a Creek Indian reservation. Congress disestablished any reservation in a series of statutes leading up to Oklahoma statehood at the turn of the 19th century. The Court reaches the opposite conclusion only by disregarding the “well settled” approach required by our precedents. Nebraska v. Parker, 577 U. S. 481, ___ (2016) (slip op., at 5).