Maryland Code, Business Regulation § 9A-506

(b)(1) A subdivision of the State which requires a local license to provide heating, ventilation, air-conditioning, or refrigeration services may not discriminate against applicants who are not residents of the subdivision.

(2) A subdivision of the State which requires a local license to provide heating, ventilation, air-conditioning, or refrigeration services shall issue a local license to any individual licensed by the Board on receipt from the individual of any application and fee required by the subdivision of the State.

(3) A subdivision of the State may not require an applicant for a local license to provide heating, ventilation, air-conditioning, or refrigeration services to take an examination if the applicant is licensed by the Board.