Cal. Welf. and Inst. Code § 226
In lieu of county juvenile justice commissions, the boards of supervisors of two or more adjacent counties may agree to establish a regional juvenile justice commission consisting of not less than eight citizens, and having a sufficient number of members so that their appointment may be equally apportioned between the participating counties. Two or more of the members shall be persons who are between 14 and 21 years of age, provided there are available persons between 14 and 21 years of age who are able to carry out the duties of a commission member in a manner satisfactory to the appointing authority. The presiding judge of the superior court with the concurrence of the judge of the juvenile court or, in a county having more than one judge of the juvenile court, with the concurrence of the presiding judge of the juvenile court of each of the participating counties shall appoint an equal number of members to the regional justice commission and they shall hold office for a term of four years. Of those first appointed, however, if the number appointed be an even number, half shall serve for a term of two years and half shall serve for a term of four years and if the number of members first appointed be an odd number, the greater number nearest half shall serve for a term of two years and the remainder shall serve for a term of four years. The respective terms of the members first appointed shall be determined by lot as soon as possible after their appointment. Upon a vacancy occurring in the membership of the commission and upon the expiration of the term of office of any member, a successor shall be appointed by the presiding judge of the superior court with the concurrence of the judge of the juvenile court or, in a county having more than one judge of the juvenile court, with the concurrence of the presiding judge of the juvenile court of the county which originally appointed such vacating or retiring member. When a vacancy occurs for any reason other than the expiration of a term of office, the appointee shall hold office for the unexpired term of his or her predecessor.
Ca. Welf. and Inst. Code § 226