The author doesn't go into great detail, but it the estimate is probably correct given the statistics of the situation. The tribes have the tribal roll with the ancestry. You can do further reading on the genetic testing and people's beliefs about their ancestry.
Yes, there are fake tribes that come out of the woodwork hoping to gain casino rights, but many if not most of these non-recognized groups often accused of being fraudulent have verifiable histories going back 100 or more years, and have been studied by historians and anthropologists (with publications to prove it). It's a shame that such groups are denied the recognition they deserve, even after all that has happened in this country.
In fact, there is no official "casino rights" recognition to seek, it's just an often unwanted right that comes along with federal tribal recognition.
So many tribes, who want other educational and or commercial benefits that come with federal recognition (like being able to label their art/crafts "Indian-made"), or who simply want the recognition due to them for reasons of ethnic pride, have to face opposition from big casino corporations worried that some tribal leader in the future might propose a casino.
There should be a form of federal recognition by BIA that doesn't involve casino rights, that's the easiest solution (although unlikely to happen for legal reasons).
I am getting a bit sick of all the FUD in this area.
The fact is, for those states that do give federally-recognized tribes casino rights (ie, most of them), there is not way for a tribe to forfeit that right.
How in the world is that a "myth" or "FUD"? Look, I can understand why you got irritated at the other statement above (of course federal recognition brings benefits other than casino rights!), but I have no idea what you would call this fact a "myth".
If you're pointing out that this would have to come from the states, and not the federal government, then it's a good point (that's what I was referring to my "legal reasons"). But why call this "FUD"?