Native American law, long a well-established practice area west of the Mississippi, is gaining ground at eastern law firms as tribes displaced in the 19th century seek to reclaim ancestral lands — and make them instantly profitable.

After the successful land-claim settlement by the Mashantucket Pequot Tribe in Connecticut, which led to the opening of Foxwoods Resort Casino in 1992, and the Mohegan Tribe’s acquisition of land in nearby Uncasville, Conn., for the Mohegan Sun Casino, other tribes have started bringing land-claim suits, and law firms are lining up to help them.