Lake County Pomo leaders are suing the county to halt a building project on a privately-owned island they hold sacred.

"I am honored to be a part of this legal case to help preserve and protect the most ancient, sacred tribal homeland island village of Elem-Modun, also known as Rattlesnake Island," Jim Brown, an Elem Indian Colony tribal leader, said in a statement.

The lawsuit was filed Friday in Lake County Superior Court by tribal members Jim and Marvin Brown and a group of supporters, Friends of Rattlesnake Island.

It contends the county should have required the island's owner, Emeryville businessman John Nady, to conduct a full environmental impact report on his plan to build a 2,000-square-foot home and a 1,000-square-foot caretaker's cabin on the island.

In September, the Board of Supervisors reversed a decision by the Planning Commission, which had required Nady to submit a full-fledged environmental impact report on the project. Instead, supervisors allowed Nady to conduct an abbreviated report that included an archaeological study of the island. In addition, county supervisors approved a work plan that requires Nady to monitor for Pomo artifacts during construction.

"That's inadequate," the plaintiffs' Sonoma County-based attorney, Susan Brandt—Hawley, said Monday.

She said the lawsuit will not address the larger issue of who rightfully owns Rattlesnake Island, but both Nady and Supervisor Rob Brown say that's what it's really about.

"The real issue is they want the island," said Nady, who purchased the 58-acre island eight years ago for $2.5 million.

His plans to build a family home on the island have been stalled by controversy since he began applying for permits to build in 2005. Elem members want the nearby island returned to them. The island served as a cultural and religious center for Pomo Indians for thousands of years and was mistakenly sold by the federal government in 1874, according to the tribe.