Possession is NOT 9/10s of the law. Never has been, There is no such law on the books. If you go into court saying possession is 9/10s of the law, don't surprised if you lose. Ask the Patrick Hiyashi who ended up with Barry Bonds' home run record ball. It bounced out of one guy's hands and Hiyashi grabbed it. In baseball, you grab it, you own it. The other guy however took Hiyashi to court saying the ball was his because it hit his hands first. To me, I would have dismissed it. The judge ordered Hiyashi to sell the ball and split the money with this other idiot. Possession is NOT 9/10s of the law. Or to put it another way, that last tenth could still fuck you.

As for land, if an Indian tribe has an old deed for land you now live on that was given to them with no intention of it ever being honored, tough shit. Say hello to your new landlords. And if they tell to get off it, get off it.

As for the masks, they must be returned as a gesture of good will. Should the Elgin marbles be returned? Yes. Greece wants them. Should the swag looted from the Summer Palace in China and now housed in the British Museum be returned? Yes. China wants it. To my knowledge, Britain has never even apologized to China for the Opium Wars--one of the worst transgressions one nation has ever forced on another. And their refusal to return looted swag from the Chinese proves their colonialist attitudes haven't changed. If they've changed then prove it.