Every insurer which withdraws as an insurer, or is required to withdraw as an insurer, from this State shall, prior to such withdrawal, discharge its liabilities to residents of this State. In the case of its policies insuring residents of this State it shall cause the primary liabilities under such policies to be reinsured and assumed by another admitted insurer. In the case of such policies as are subject to cancellation by the insurer, it may cancel such policies pursuant to the terms thereof in lieu of such reinsurance and assumption.