riot, rout, and unlawful assembly, in law, varying degrees of concerted disturbance of the peace. At common law, an unlawful assembly is a gathering of at least three persons whose conduct causes observers to reasonably fear that a breach of the peace will result. When the meeting is a furtherance of a criminal conspiracy, the participation of only two persons will suffice to constitute the crime of unlawful assembly. Under British law, the Riot Act (1716) required that a sheriff, judge, or other authority appear before an unruly crowd and read a declaration ordering them to disperse, on penalty of arrest. Modern statutes have freed the crime of unlawful assembly from some of its technicalities. Thus, there are municipal ordinances that make unlawful an unlicensed street assembly that blocks traffic even if there is no danger of tumult. An unlawful assembly becomes a rout when the participants take some step to achieve their common purpose; e.g., if three men who have assembled to commit arson proceed toward the building that they intend to set on fire, they are guilty of a rout even if they never reach their goal. There is a riot if violence actually results from an unlawful assembly. If a police officer (or other officer of the peace) commands bystanders at a riot to help him in repressing it, they must obey on pain of themselves being deemed rioters. The First Amendment to the U.S. Constitution protects the "right of the people peaceably to assemble," and has provided protection for many types of assembly, including some forms of picketing and demonstrations.