Maryland Code, Insurance § 4-101

(a)(1) Except as otherwise provided in this article, a person may not act as an insurer and an insurer may not engage in the insurance business in the State unless the person has a certificate of authority issued by the Commissioner.

(2) An insurer may not have or maintain in this State an office, representative, or other facility to solicit or service any kind of insurance in another state unless the insurer is then authorized to engage in the same kind of insurance business in this State.

(1) transactions that relate to policies that were lawfully written in the State, or the liquidation of assets and liabilities of the insurer, including the collection of premiums on existing policies, resulting from former authorized operations of the insurer in the State;

(2) transactions that occur after issuance of a policy that covers only subjects of insurance not resident, located, or expressly to be performed in the State at the time of issuance, or that covers property in the course of transportation by land, air, or water to, from, or through the State, including any incidental preparation and storage, and the coverage was lawfully solicited, written, and delivered outside the State;

(3) transactions that relate to surplus lines coverages lawfully written under Title 3, Subtitle 3 of this article; or

(4) reinsurance transactions, except as to domestic reinsurers.