California Labor Codes 5270.5
§ 5270.5 List of eligible arbitrators
(a) The presiding workers' compensation judge at each district office shall prepare a list of all eligible attorneys who apply to be placed on the list of eligible arbitrators. Attorneys are eligible to become arbitrators if they are active members of the California State Bar Association and are one of the following: (1) A certified specialist in workers' compensation, or eligible to become certified. (2) A retired workers' compensation judge. (3) A retired appeals board member. (4) An attorney who has been certified to serve as a judge pro tempore.
(b) No attorney shall be included in a panel of arbitrators, if he or she has served as a judge in any proceeding involving the same case, or has represented, or whose firm has represented, any party in the same case.