D.C. Mun. Regs. tit. 24 § 2100
When fires, accidents, wrecks, explosions, parades, or other occasions cause or may cause persons to collect on the public streets, alleys, highways, or parkings, the Chief of Police, an inspector or captain of the police, or an officer acting for him or her may establish an area or zone that he or she considers necessary for the purpose of affording a clearing for the following:
Each person present at the scene of an emergency occasion shall comply with any necessary order or instruction of any police officer.
No person shall enter the emergency area or zone unless duly authorized by the person in command of the emergency occasion, except as provided in § 2100.4.
Bona fide representatives of the press, bona fide insurance adjusters or underwriters, and other persons that the Chief of Police may authorize to be within the emergency area or zone shall be permitted within the lines established by the Police Department under the conditions set forth in § 2100.5 and §§ 2101 through 2103.
Persons entering the emergency area or zone under § 2100.4 shall have plainly exposed to view the press pass or fire pass issued under the provisions of §§ 2101 through 2103.
D.C. Mun. Regs. Tit. 24, § 2100