Md. Code, Public Safety § 3–309

(a) Within 30 days after issuance of a commission and before performing the duties of a special police officer, each special police officer shall take the oath required by Article I, § 9 of the Maryland Constitution before the clerk of the circuit court where the commission is received.

(b) The clerk of the court shall transmit to the Secretary of State a certificate that indicates that the special police officer has taken the oath required by subsection (a) of this section.