No provision in an automobile liability policy or endorsement for such coverage effective in this state issued by an insurer on and after the effective date of this act¹ which grants the insurer the right of subrogation for payment of benefits under the expenses for the medical services coverage portion of the policy, to a named insured under the policy, or to any relative of the named insured who is a member of the named insured's household shall be valid and enforceable; provided, that such policy or endorsement may provide for said insurer's rights of subrogation and setoff upon such payments to any person who is not a named insured under the policy or a relative of the named insured who is a member of the named insured's household.