California Code, Corporations Code - CORP § 18015

(a) If the governing principles of an unincorporated association define the membership of the association, “member” has the meaning provided by the governing principles.

(b) If the governing principles of an unincorporated association do not define the membership of the association, “member” means a person who, pursuant to the governing principles of the unincorporated association, has a right to participate in the selection of persons authorized to manage the affairs of the unincorporated association or in the development of policy of the unincorporated association, but does not include a person who participates solely as director, officer, or agent of the association.