It is not nearly common enough knowledge that most Native tribes in the U.S. don't actually own all of the land within their reservation. There are millions of acres of reservation land that tribes don't legally own and they have no control over how that land is used. Like, there are a lot of different concepts tied in with the land back movement, but a major one is literally just getting reservation land back into tribal ownership.
I’m assuming your talking about the tremendous disaster that is the fractional inheritance of land in reservations that has been forcibly divided between exponential heirs, making the management of land impossible as 40 acres could have more than 400 owners, that are required to come to a consensus to do anything. To quote from the fantastic book “Mine!” “6 million acres of native land have been tied up in 100 000 fractionated tracks, owned by 250 000 land owners, holding 2.5 million fractional interests.”
The amount of money that is spent tracking the tiny percentages random descendants own that could be spent improving Native American life is astounding.
Yeah, fractionated land is an absolute nightmare in the management of tribal land that I could do a whole rant about (what do you mean someone inherited 0.0000002% of 40 acres and it's worth 12¢, the postage alone to notify all the relevant parties cost 1000 times as much, I can't believe I have to waste my work hours on processing this bullshit).
But I was referencing the way more basic fact that many tribal governments literally do not own all of the land within the reservations that were guaranteed to them in treaties. There are prime parcels owned by private white land owners or the government smack dab in the middle of reservations. And those private land owners legally don't need to get permission from the tribal government to do whatever they want with their land.
"But isn't the whole point of reservations is that they're land that's been, well, reserved for Native Americans?" Yeah, that's what the treaties say, but the US doesn't exactly have a great track record with honoring those.