A certificate of authority shall not be required of an insurer, not otherwise authorized in this state, as to the following transactions:
(1) transactions relative to its policies lawfully written in Montana or liquidation of assets and liabilities of the insurer (other than collection of new premiums), all as resulting from its former authorized operations in Montana;
(2) transactions relative thereto subsequent to issuance of a policy covering only subjects of insurance not resident, located, or expressly to be performed in Montana at time of issuance, and which coverage was lawfully solicited, written, and delivered outside Montana;
(3) transactions pursuant to surplus lines coverages lawfully written pursuant to part 3 of this chapter;
(4) reinsurance, except as to domestic reinsurers.