Md. Code, Land Use § 17–303

(a) The park police have concurrent general police jurisdiction with the Montgomery County and Prince George’s County police:

(1) within the parks and other areas under the jurisdiction of the Commission;

(2) within buildings under the jurisdiction of the Commission; and

(3) on the portion of all roads and sidewalks immediately adjacent to property under the jurisdiction of the Commission.

(b) (1) The park police have jurisdiction off park property that may be provided by any reciprocal agreement entered into under § 2–105 of the Criminal Procedure Article.

(2) A reciprocal agreement shall specify the circumstances under which a park police officer may make arrests off of park property.

(3) Notwithstanding § 2–105 of the Criminal Procedure Article, a reciprocal agreement may allow arrests in emergency or nonemergency situations.