Cal. Ins. Code § 940

The commissioner shall accept and hold securities in trust for the policyholders or policyholders and creditors of an insurer and for their benefit, whenever (a) the law of another state or of a foreign country requires such a deposit with an officer of this state as a prerequisite to transacting insurance business in that state or country, or (b) the law of this state requires such a deposit with an officer of this state.