A domestic stock insurer shall have the right to purchase or acquire shares of its own stock only as follows:
1. For elimination of fractional shares.
2. Incidental to the enforcement of rights of the insurer with respect to lawful transactions previously entered into in good faith for purposes other than the acquisition of such shares.
3. For the purposes of a general savings and investment plan for employees or agents of the insurer.
4. For mutualization of the insurer, as provided in section 3472.
5. For retirement or otherwise of the shares under a plan submitted to and approved in writing by the superintendent. The superintendent may not approve a plan unless found by the superintendent to be reasonable, fair and equitable as to remaining stockholders of the insurer, and not materially adverse to the protection of the insurer's policyholders.