SACRAMENTO—An arbitrator on Monday rejected all of Joe Dunn’s remaining claims against the California state bar, ending a three-year legal saga that pit the one-time executive director against his former employer.

The arbitrator, Edward Infante, a former chief magistrate judge of the U.S. District Court for the Northern District of California, said Dunn failed to prove his November 2014 firing was retaliation for his allegations that the Office of Chief Trial Counsel was manipulating disciplinary backlog numbers.