You’d be surprised how many tribes are working on expanding their land base. Of course they want more land; the whole continent used to be theirs, and they’d like to get as much back as they can. Those who have strong economic development are quietly buying up rural land, mostly outside of, but contingent to, the reservation. Others may be buying back some of the private land within the rez, but I haven’t heard of that. Sounds like a good idea, though. Non-private tribal land is owned by the federal gov’t. The tribes can’t sell it without arranging with the feds to take it out of trust status and make it private. I’ve never heard of that, I’m not even sure the feds would allow it. But maybe there have been some cases of that, somehow.
Tribal courts can only try tribal members, by federal law. Non-Natives who commit crimes inside the rez fall under state jurisdiction, unless they commit a federal crime, then the FBI steps in. The 7 Major Crimes Act puts Natives under the FBI’s jurisdiction for the most heinous crimes: murder, attempted murder, rape, attempted rape, and 3 others. Tribal justice actually tends to be lax by non-Native standards, and follows Native custom. For example, a tribe near where I live tried a guy who had molested two little girls. Since the crime involved non-Natives, he was first tried in state court, and found not guilty due to lack of evidence. The tribe got hold of him, tried him, and required him to take over the spiritual duties of his elderly father. The perp was next in a lineage of ceremonial leaders, so the tribe made him learn everything he had to learn to carry out the ceremonial traditions, and take over his father’s duties. Amazingly, it turned him around. He really mellowed out.
The US Constitution doesn’t apply in “Indian Country” (that’s a legal term). Indian preference hiring is required even off-rez, in any situation where federal funds earmarked for Indians are used. If a university professor gets federal funds to research some Indian-related issue, and wants to hire a grad student to help, he’s required to give first consideration to Native grad students. If none are qualified, the position can go to a non-Native.
Non-Natives living inside the rez, even if they own land, aren’t allowed to vote in tribal elections. Only tribal members can vote. (Non-member Indians also can’t vote.) But the tribe can tax them.
The tribes have the power to exclude people from the rez. Technically, they could require visas and set up immigration check-points, but that’s very expensive, nobody can afford it. But if a non-Native really ticks the tribe off, like an author in NM who published a stupidly stereotypical and insulting book on the tribe, they can be banished for good. On the other hand, if they like you, they’ll hire you, Indian preference hiring law nothwithstanding.
There are lots of books on Federal Indian law. Check it out–it’s fascinating.