Cal. Ins. Code § 1600

The commissioner shall require every foreign insurer, as a condition precedent to receiving and holding a certificate of authority, to file and maintain in the commissioner’s office a writing designating an agent for service of process. The agent designated may be any person residing in this state, including, but not limited to, any corporate officer of the insurer. The writing shall state the name of the agent and his or her place of business in this state with sufficient particularity so that he or she can readily be found by peace officers or process servers. Appointment of an agent reasonably available for service of papers, notice, proof of loss, summons or other process during business hours shall be continuously maintained by every admitted insurer subject to this article while it holds a valid and unrevoked certificate of authority.