Md. Code, Family Law § 9–303

(a) This section applies if there is a conflict between a custody order of a court of this State and a custody order of a court of another state.

(b) Except as provided in subsection (c) of this section, a custody order of a court of this State prevails over a custody order of a court of another state.

(c) A custody order of a court of another state prevails over a custody order of a court of this State if the court in the other state passed its custody order:

(1) after the custody order was passed by a court of this State; and

(2) in proceedings in which the lawful custodian under the custody order of a court of this State:

(i) consented to the custody order passed by the court of the other state; or

(ii) participated personally as a party.