Cal. Ins. Code § 5090
Any person having an insurable interest in property in the county in which any such insurer is formed or any person having such an interest in property in any adjoining county may become a member by insuring therein. Every member shall be entitled to all the rights and privileges appertaining to membership, except that at least a majority of the directors shall reside either in the county in which the insurer is formed or in any of the counties which were the original domicile of any of the constituent companies of a county mutual merged under Article 9.5 (commencing with Section 7040) of this chapter, and not more than one member from each of the adjoining counties in which it transacts insurance may become one of its directors. Whenever any public or private corporation, board or association in this State has entered into an agreement for and holds a policy in any county mutual insurer operating under this chapter, any officer, stockholder or trustee of any such corporation, board or association may be recognized as acting for or on its behalf for the purpose of such membership, but shall not be personally liable upon such contract of insurance by reason of acting in such representative capacity. The right of any corporation organized under the laws of this State to participate as a member of such county mutual insurer is hereby declared to be incidental to the purpose for which such corporation is organized and as much granted as the rights and powers expressly conferred.
Ca. Ins. Code § 5090