Cal. Gov. Code § 3524.57

Employee organizations shall have the right to represent their members in their employment relations with the Judicial Council, except that once an employee organization is recognized as the exclusive representative of an appropriate unit, the recognized employee organization is the only organization that may represent that unit in employment relations with the Judicial Council. Employee organizations may establish reasonable restrictions regarding who may join and may make reasonable provisions for the dismissal of individuals from membership. This section shall not prohibit any employee from appearing in his or her own behalf in his or her employment relations with the Judicial Council.