Clay County Attorney Michael Zenor resigned two days before a Supreme Court panel recommended a public reprimand.
Zenor had been the county's top prosecutor for 26 years.
The Grievance Commission of the Supreme Court of Iowa concluded last week that Zenor appeared to work on behalf of people charged with traffic violation while also serving as the county attorney.
Zenor has a private law practice in addition to his employment with Clay County.
The commission ruled that Zenor's work in three cases violated state disciplinary rules pertaining to conflicts of interest. The commission said the violations were considered "especially serious given that he is the top law enforcement officer in the county. As an employee of Clay County, he has a duty to all citizens not to represent conflicting interests."
The commission's recommendation for a public reprimand goes to the Iowa Supreme Court for a decision on the final action to be taken.
Zenor's resignation is scheduled to take effect June 7.
Assistant County Attorney Mike Houchins said Zenor's resignation was not related to the commission's findings. Instead, Houchins said Zenor had anticipated leaving office before his current term expired on Dec. 31, 2006, to move to neighboring Dickinson County.
Iowa law requires that county attorneys live in the counties they serve.