Officers of the National Guard and naval militia shall be appointed by the Governor, subject to the procedure prescribed in regulations of the United States Department of Defense relating to the National Guard and naval militia. The rule of seniority shall be followed when practicable. Only such officers shall be commissioned in the National Guard and naval militia as have successfully passed the tests and examinations as to physical, moral and professional fitness prescribed by the laws and regulations of the United States relating to the qualifications of National Guard or naval militia officers. Officers of the organized militia, as provided for in § 27-2, shall be appointed in accordance with regulations approved by the Governor.