Oklahoma used to be "Indian Territory". In the 1830s the USA ethnicly cleansed the eastern US of indigenous people and death-marched them to the west, dumping the survivors on the (then) border. Naturally, it signed treaties, promising that they would be left free to govern themselves, particularly in matters of criminal law. Then, in the early twentieth century, white people decided they wanted that land too, so they turned Oklahoma into a state. A bit over a century later, that state arrested, prosecuted, and purportedly convicted a child molester and a murderer. Naturally, they challenged their convictions. Their ultimate challenge was to assert that the state lacked jurisdiction, because they were members of a particular Native American tribe and their crimes had been committed on tribal land: when Congress turned Oklahoma into a state, it didn't extinguish tribal sovereignty over criminal law. And the Supreme Court looked at the law, and said "yep":
Today we are asked whether the land these treaties promised remains an Indian reservation for purposes of federal criminal law. Because Congress has not said otherwise, we hold the government to its word.
(If this sounds familiar, its because we've seen it before, in a different context, in Ngati Apa v Attorney-General, AKA the foreshore and seabed case. Like history, the law rhymes).
But while its ostensibly about criminal law and a particular tribe - the Muscogee (Creek) Nation - the decision goes wider. Because the Muscogee aren't the only nation covered by this particular set of treaties, and it raises the question of what else Congress didn't extinguish when it forced statehood upon them. And this affects the entire eastern half of Oklahoma.
Unlike New Zealand, the US has a long history of overlapping jurisdictions and tribal law. Even if their treaties have mostly been repeatedly broken and over-ridden and ignored by the federal government, there's enough of a remnant that they actually have the tools to deal with this in a just and respectful manner if they want to. The question now is whether they will, or whether they'll lose their shit at the idea that a indigenous person somewhere has some rights, and legislate to take them away like we did.