The question before the court in Carpenter v. Murphy is whether Congress disestablished the reservation of the Muscogee (Creek) Nation in the early 20th century. If not, that reservation created in 1866 still exists and major crimes involving tribal members in that region of eastern Oklahoma must be prosecuted in federal courts, not state courts.
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Much of Tuesday's hour of arguments focused on the practical implications of a ruling in favor of the tribe. Several justices showed deep concern about the ramifications of a ruling in favor of the Creeks.
“There are 1.8 million people living in this area,” said Justice Stephen Breyer. “They have built their lives not necessarily on criminal law but on municipal regulations, property law, dog-related law, thousands of details. And now, if we say really this land ... belongs to the tribe, what happens to all those people? What happens to all those laws?”
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Justice Neil Gorsuch, a President Donald Trump appointee, did not participate in Tuesday's arguments and will not take a side in an eventual opinion because he was on the 10th Circuit last year when it ruled that the Creek reservation still exists.
The population of Oklahoma is about 3.9 million people, so this affects a large percentage of them in some way.
The Trump administration sided with the state of Oklahoma:
Last August, the 10th Circuit Court of Appeals overturned the murder conviction and death sentence of Patrick Murphy, who was convicted in state court of mutilating and murdering George Jacobs in 1999. The court ruled the Creek reservation still exists and Murphy therefore must be tried in federal court for the murder on reservation land.
The Justice Department's arguments were three-pronged: Congress abolished the Creek reservation, the 10th Circuit erroneously cherry-picked historical documents to conclude it didn't, and Oklahoma had jurisdiction in the Murphy case regardless.
“Congress granted the state jurisdiction to prosecute crimes involving Indians in the former Indian Territory as part of the series of acts leading to Oklahoma statehood,” Francisco wrote.
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The states of Nebraska, Kansas, Louisiana, Michigan, Montana, South Dakota, Texas, Utah and Wyoming filed a brief Monday asking the Supreme Court to side with Oklahoma, concerned tribal lands in their states could also be affected.
If you are interested, Mvskoke News, the newspaper of the Muscogee (Creek) Nation, provides some historical background to the case.
They also give some details on 6 amicus briefs filed in the case.

