McGirt v. Oklahoma, 591 U.S. ___ (2020), was a landmark[1][2] United States Supreme Court case which held that the domain reserved for the Muscogee Nation by Congress in the 19th century has never been disestablished and constitutes Indian country for the purposes of the Major Crimes Act, meaning that the State of Oklahoma has no right to prosecute American Indians for crimes allegedly committed therein.

The Oklahoma Court of Criminal Appeals applied the McGirt rationale to rule nine other Indigenous nations had not been disestablished.

In these cases, jurisdiction properly vests within the Indigenous judicial systems and the federal district courts under the Major Crimes Act.

[3][4] Consistent with McGirt, this initially included crimes perpetrated against American Indian victims by non-Indian defendants.

Prior to its statehood in 1907, about half of the land in Oklahoma, including the Tulsa metro area today, had belonged to the Five Civilized Tribes: the Cherokee, Choctaw, Chickasaw, Creek (now Muscogee), and Seminole tribal nations, whose nickname arose from their adoption of Anglo-American culture.

[8] Eventually, these conflicts led to the Trail of Tears, an over 1,000 mile march from the Eastern US to Oklahoma that the US Government required the Native Americans to endure, resulting in the establishment of reservations.

Ian Gershengorn, former Solicitor General of the United States, argued the case, after offering his services to the plaintiff.

The 5–4 majority opinion was written by Justice Neil Gorsuch and joined by Justices Ruth Bader Ginsburg, Stephen Breyer, Sonia Sotomayor, and Elena Kagan, and determined that for purposes of the Major Crimes Act, Congress had failed to disestablish the Indian reservations and thus those lands should be treated as "Indian country".

Gorsuch wrote, "Today we are asked whether the land these treaties promised remains an Indian reservation for purposes of federal criminal law.

Roberts wrote of the majority decision, "The state's ability to prosecute serious crimes will be hobbled and decades of past convictions could well be thrown out.

[22][23] The majority decision left open other potential impacts between territorial rights that may arise, which the Court put to the state and the tribes to resolve amicably should conflicts occur.

[37] McGirt pled guilty prior to the new trial in December 2023,[38] and his sentence was reduced to 30 years with time served credited, allowing for his release in May 2024.

Further complicating matters was the March 2021 decision of the Oklahoma Supreme Court in the case of Shaun Bosse, a non-tribal state resident who had been convicted of the murder of a Chickasaw family on tribal lands in 2012.

[41] The Oklahoma Supreme Court ruled that under McGirt, Bosse must be tried under federal law as well since the victims were Native American.

Hunter filed an emergency request with the U.S. Supreme Court beseeching the judges to intervene and reconsider their McGirt decision.

[48] In an attempt to overturn the McGirt ruling, either partially or in its entirety, the state filed a new petition to the Supreme Court in the Oklahoma v. Castro-Huerta case.

In April 2021, the Oklahoma Court of Criminal Appeals overturned the sentencing due to jurisdiction issues raised in McGirt.

[50] On June 29, 2022, the Court held in Castro-Huerta that Federal and State governments have concurrent jurisdiction to prosecute crimes committed by non-Native Americans against Natives on tribal land.

Kavanaugh wrote an opinion on the case, joined by Alito, suggesting that there may be further need to review the bounds of McGirt with municipal laws.