Cal. Insurance Code § 11072

A domestic society may, by a reinsurance agreement, cede any individual risk or risks in whole or in part to an insurer having the power to make such reinsurance and authorized to do business in this State, or if not so authorized, one which is approved by the commissioner; but no such society may reinsure substantially all of its insurance in force without the written permission of the commissioner. It may take credit for the reserves on such ceded risks to the extent reinsured, but no credit shall be allowed as an admitted asset or as a deduction from liability, to a ceding society for reinsurance made, ceded, renewed, or otherwise becoming effective after the effective date of this chapter, unless the reinsurance is payable by the assuming insurer on the basis of the liability of the ceding society under the contract or contracts reinsured without diminution because of the insolvency of the ceding society.