The purpose of this subchapter is to provide orderly and uniform procedures, as required by law and dictated by sound public policy, for any authorized insurer or HMO filing a plan of withdrawal with the Commissioner of Insurance under Insurance Code Chapter 827. Nothing in this subchapter authorizes or allows an insurer or HMO to withdraw from any coverage if such withdrawal would violate any federal or state law or any provisions contained in a contract or evidence of coverage or a policy or certificate of insurance itself.