The criminal offense of unlawful assembly generally means the assembly of multiple persons resulting in conduct that (1) is intended to commit a breach of the peace or other unlawful act; (2) creates an immediate danger of damage to property or injury to persons; (3) substantially obstructs law enforcement or other governmental functions or services; (4) is tumultuous or violent and likely to cause public alarm; or (5) deprives any person of a legal right or disturbs any person in the enjoyment of a legal right by using force or the threat of force.

Unlawful assembly laws vary from state to state and some states have related offenses such as rioting, riots and routs, participating in a riot, inciting a riot, failing to disperse, and disturbing the peace. The criminal offense of unlawful assembly may be included in the definition of one or more of these offenses or may be a separate criminal offense. These laws are generally located in a state’s statutes—often in the penal or criminal code.

In Utah, the criminal offense of unlawful assembly is addressed under Utah Code § 76-9-101. According to this statute, a person is guilty of unlawful assembly if they intentionally or knowingly assemble with other persons and agree to engage in conduct constituting a breach of the peace, or if the assembly is likely to cause a breach of the peace. The law also covers situations where the assembly results in conduct that creates an immediate danger of damage to property or injury to persons, substantially obstructs law enforcement or other governmental functions, or is tumultuous or violent and likely to cause public alarm. Additionally, if the assembly involves using force or the threat of force to deprive any person of a legal right or disturb any person in the enjoyment of a legal right, it may also be considered unlawful. Penalties for unlawful assembly can range from a class B misdemeanor to higher charges if the assembly leads to more serious offenses. Utah's statutes also cover related offenses such as rioting and failure to disperse, which are outlined in separate sections of the penal code.