Cal. Sts. & Hy. Code § 2553
An authority, other than the Metropolitan Transportation Commission or a county transportation commission or a council of governments designated pursuant to Section 2551, shall have seven members, with two members selected by the board of supervisors and five members selected jointly by the city councils of cities within the county.
If the Metropolitan Transportation Commission functions as a service authority, it shall consist of all the members of the commission as set forth in Section 66503 of the Government Code.
If the Sacramento Area Council of Governments functions as a service authority, it shall consist of (a) all of the members of the board of directors of the council, as set forth in the Joint Powers Agreement of the Sacramento Area Council of Governments, dated October 21, 1980, pursuant to Chapter 5 (commencing with Section 6500) of Division 7 of Title 1 of the Government Code, (b) one member representing San Joaquin County, (c) one member representing the cities of San Joaquin County, (d) one member representing any other county that is not already a member of the council, and (e) one member representing the cities within that county.
Ca. Sts. and High. Code § 2553