In his pocket of eastern Washington, where sweet corn and potato fields stretch for miles, Sheriff Dale Wagner of Adams County talks about immigration enforcement in solemn terms like oath and duty.

But precisely whom Sheriff Wagner has a duty to serve and obey is a question that has put him at odds with the state’s top law enforcement official and thrust the two of them into an escalating debate over what role local and state authorities should play in helping enforce immigration law.

Nick Brown, Washington’s attorney general, has accused Sheriff Wagner in a lawsuit of sharing inmate information with federal immigration agents in defiance of a state law meant to limit collaboration between Washington’s law enforcement officers and federal immigration agencies.

In an interview in his office in the city of Othello, Sheriff Wagner defended providing inmate information to federal agents, saying he was within his authority and that he was doing what he needed to do to protect his constituents.

“It goes back to my oath,” he said. “I protect the State of Washington’s Constitution as best I can, and the United States Constitution as best I can, and that’s all I can do.”

The lawsuit also alleges that deputies in his office have been holding people in jail based solely on immigration status, and that deputies have been allowing such prisoners to be interrogated by federal agents — allegations that Sheriff Wagner said were untrue.