(1) The commissioner shall revoke the authority of a domestic mutual insurer so to extinguish the contingent liability of its members if

(a) at any time the insurer's assets are less than the sum of its liabilities and the surplus required for such authority, or

(b) the insurer, by resolution of its directors approved by its members, requests that the authority be revoked.

(2) Upon revocation of such authority for any cause, the insurer shall not thereafter issue any policies without contingent liability, nor renew any policies then in force without written endorsement thereon providing for contingent liability.