Maryland Code, Public Safety § 2-418

(a)(1) Except as otherwise provided in paragraphs (2) and (3) of this subsection, a police employee who resigns from the Department for any reason may not be reappointed.

(2) A police employee who resigns to enter military service may be reappointed.

(3) By rule, the Secretary may reappoint a police employee who resigned in good standing if the individual meets the requirements then applicable for initial appointment.

(4) An individual may not be reappointed to a rank higher than the rank that the individual previously held as a police employee.