Cal. INS § 4097

(a) A domestic incorporated medical malpractice mutual insurer, issuing nonassessable policies on a reserve basis may be converted into an incorporated stock insurer issuing, on a reserve basis, nonassessable policies either by demutualization or by establishing a mutual holding company. To that end, it may provide and carry out a plan for the conversion by complying with the requirements of this article. (b) A mutual holding company may be converted into a stock corporation. To that end, it may provide and carry out a plan for the conversion by complying with the requirements of this article. (c) As part of the conversion authorized in this section, a domestic incorporated medical malpractice mutual insurer may merge with an incorporated stock insurer, if the merging insurers comply with the provisions of Article 9 (commencing with Section 4090) applicable to their participation in the merger, or may transfer its domicile to any other state, if the insurer complies with Section 709.5.