First of all, I know the person who sold the meteorite as well as the some of the people who bought the larger piece that was auctioned off (I've even helped the lead investor work on his meteorite website) so I do know a bit more about this situation than most people here probally do. Ok, now that I've got that out of the way......
This is one of the biggest loads of crap I've ever heard of. First of all, the history of this meteorite is that it some guy found it on a steel company's land, dragged it to his land, charged people to see it, steel company figured out that it was stolen, sued to get it back, won, sold it to a wealthy lady in New York who donated it to the museum in NYC. Its been there since the 1920's. The indians didn't say anything what so ever until the 90's when they sued the museum to get ownership of it. I've heard that they would have chopped some of it up themselves to sell it. Daryll Pitt (the gentleman who sold the meteorite) had offered to sell it the tribe for a very reduced price to the tribe but they refused to do so because they said that they didn't want to contribute to the "commercialization of their herritage" (their words, not mine). No, they wanted the meteorite for free. While they may not have the meteorite on their land anymore they have access to the meteorite at anytime they want for their ceremonies and the AMNH fund college scholarships for multiple young people of the tribe. Basically, the indians are just being greedy here. When the meteorite was taken from Oregon quite a while back they didn't say anything about it. They're mainly bitching and whining about who gets to use the nice big rock for tourism.
As for how the AMNH could do something like this is easy. Large institutions like that will trade with private individuals all the time. Hell, I've got a slice of an extremely rare meteorite that I got from the Smithsonian. Why do they do this? They have large collections of meteorites, most of which are rather uninteresting scientifically and don't have much scientific value (much like this meteorite). Not only do most museums display their meteorite collection they also do research on them. In this case the museum had cut a large piece of the meteorite off so that they could mount it on a very nice display. Really not that big of a deal at all as meteorites are cut all the time. So, the museum had a decent sized chunk of a meteorite that really doesn't have that much scientific value (its a fairly common type of iron meteorite that's very weathered) when a new meteorite from Mars was discovered in the Los Angeles area that's fairly unique and many people were falling over each other to get too (I've got about 10 milligrams of it myself). Daryll obtained a good sized piece of the Mars rock from the finder and instead of selling all of it on the open market to private collectors (who would easily pay $2,500 a gram) he went around to various museums of the world and traded with them. What did he trade? His valuable (both commercially and especially scientifically) Mars rock in exchange for rather boring scientifically speaking but incredibly valuable commercially that various museums would be happy to trade away. Basically, the museum in NYC got an important Mars rock that it has performed extensive research on in exchange for a rather boring rock that they've already done just anything they would want to do to. Daryll suplies valuable research material to the scientific community (which he could have very easily sold to private collectors) and obtains a scientifically boring rock that some rather greedy indians happen to attach some scientific value to. He's a pretty good guy who just happens to get crap from greedy indians.
What I find really interesting is the fact that they make such a big fuss about this well known meteorite but really haven't said anything at all about the much much much more interesting and scientifically valuable one that was found in one of their burial grounds and has since been sliced up and distributed around the world (including a small piece in my living room).
By the way, if anyone wants some of the rusted fragments of the meteorite that started this discussion let me know as I can get them for you. Hell, if you want any other meteorites let me know too! Chances are I can get them one way or another.
I don't need to fight
To prove I'm right
I don't need to be forgiven.