Under Pennsylvania law, an insurer that has not obtained a certificate of authority from the Insurance Commissioner before transacting insurance in the Commonwealth is best described as:

Why this is the answer

40 P.S. § 46 makes it unlawful for any insurer of another state or foreign government to transact business in Pennsylvania without first obtaining a certificate of authority from the Insurance Commissioner. An insurer holding such a certificate is 'authorized' or 'admitted.' Domestic, foreign, and alien refer to the insurer's state or country of domicile, not its admission status. An accredited reinsurer is a separate credit-for-reinsurance concept. Therefore, the proper PA label for an entity transacting insurance in the Commonwealth without a PID certificate of authority is 'unauthorized insurer.'