D.C. Code § 5-205

The Director of the National Park Service, in his discretion, may appoint special policemen, without compensation, for duty in connection with the policing of the public parks and other reservations under his jurisdiction within the District of Columbia, such special policemen to have the same powers and perform the same duties as the United States Park Police and Metropolitan Police of said District of Columbia, and to be subject to such regulations as he may prescribe; provided, that the jurisdiction and police power of such special policemen shall be restricted to the public parks and other reservations under the control of the Director of the National Park Service.