Rule 51:3.9 Service as Arbitrator or Mediator forbids judges from acting as either an arbitrator or mediator apart from their official judicial duties.
Iowa Supreme Court Rules: Chapter 51 - Iowa Code of Judicial Conduct
Iowa Supreme Court. Jan. 1, 2020https://www.iowacourts.gov/static/media/cms/Chapter51IowaCodeofJudicialConduct_1B34466ABBED7.pdf