PORTLAND— Mia Prickett’s ancestor was a leader of the Cascade Indians along the Columbia River and was one of the chiefs who signed an 1855 treaty that helped establish the Confederated Tribes of the Grand Ronde in Oregon.

But the Grand Ronde now wants to disenroll Prickett and 79 relatives, and possibly hundreds of other tribal members, because they no longer satisfy new enrollment requirements. Prickett’s family is fighting the effort, part of what some experts have dubbed the “disenrollment epidemic” — a rising number of dramatic clashes over tribal belonging that are sweeping through more than a dozen states, from California to Michigan.The enrollment battles come at a time when many tribes — long poverty-stricken and oppressed by government policies — are finally coming into their own, gaining wealth and building infrastructure with revenues from Indian casinos. Critics of disenrollment say the rising tide of tribal expulsions is due to greed over increased gambling profits, along with political in-fighting and old family and personal feuds. Since the 1990s, Indian gambling revenues have skyrocketed from $5.4 billion to $27.9 billion in 2012.