CA Ins Code Section 4097.05

A plan of conversion adopted by a medical malpractice mutual insurer to establish a mutual holding company shall provide that the medical malpractice mutual insurer will become a stock insurer, that the members of the medical malpractice mutual insurer will become members of a mutual holding company, that the mutual holding company will acquire at least 51 percent of the voting stock of the stock holding company, and that the stock holding company will acquire all of the voting stock of the converted insurer.