TUCSON, Ariz. — The heat in the Sonoran Desert neared 100 degrees on the day several years ago when Border Patrol agents at a checkpoint pulled over an elderly Hispanic man, dressed impeccably in a tailored suit.

They ordered him out of his vehicle and requested his identity papers, which showed that he was a Mexican-born immigrant named Raúl H. Castro. He had turned 96 that very day.

Ana Doan, a longtime friend who was driving him to a birthday celebration in Tucson, pleaded without success to be allowed to give him some water.

“I was screaming at the agents, telling them they were holding the former governor of the state of Arizona,” she said.