25 CFR § 11.442 - Riot; failure to disperse.
(a) A person is guilty of riot, a misdemeanor, if he or she participates with two or more others in a course of disorderly conduct:
(1) With purpose to commit or facilitate the commission of a felony or misdemeanor; or
(2) With purpose to prevent or coerce official action; or
(3) When the actor or any other participant to the knowledge of the actor uses or plans to use a firearm or other deadly weapon.
(b) Where three or more persons are participating in a course of disorderly conduct likely to cause substantial harm or serious inconvenience, a law enforcement officer may order the participants and others in the immediate vicinity to disperse. A person who refuses or knowingly fails to obey such an order commits a misdemeanor.