California Code, Insurance Code - INS § 1312

(a) Any reciprocal or interinsurance exchange, domestic or foreign, which has obtained a certificate of capability to reinsure or a favorable order under Section 1401.5 and whose subscribers by such order have no liability for assessment, may accept reinsurance of risks for all classes of insurance which it writes in California including the class in which such reinsurance is to be accepted.

(b) Contracts accepting such reinsurance shall be entered into between the ceding insurer and the reinsuring reciprocal or interinsurance exchange by its attorney in fact. The ceding insurer need not become a member of or a subscriber to the reinsuring reciprocal or interinsurance exchange and such contracts of reinsurance may contain any or all of the terms and conditions customary in reinsurances of the classes of insurance covered.