Arthur Lazarus, a lawyer and champion of legal rights for Native Americans, who won a landmark award for the Sioux Nation in its continuing struggle involving the Black Hills of South Dakota, died on July 27 in Washington. He was 92.

The cause was complications of kidney and heart disease, his son Edward said.

Over six decades, Mr. Lazarus helped Native American tribes across the country develop democratic institutions, reclaim lands and exercise sovereign powers.

His work was made possible by the Indian Reorganization Act of 1934, known as the “Indian New Deal.” The act reversed decades of assimilationist policies of the United States government and allowed tribes to re-establish their tribal governments and cultures. Mr. Lazarus guided them in these efforts.

“Like any fledgling government, they needed help,” Edward Lazarus, who is also a lawyer and has written about Indian issues, said in an interview. “That meant developing a taxation system on the reservations, setting up a civil justice system, capturing water and mineral rights, and sometimes suing or negotiating with the United States government.”