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 Illinois, the criminal offense of unlawful assembly is addressed under 720 ILCS 5/25-1 of the Illinois Compiled Statutes, which defines the crime of mob action. Mob action can occur when two or more persons assemble with the intent to commit an unlawful act, or when such an assembly results in the use of force or violence that disturbs the public peace. This statute encompasses several of the elements described in the general definition of unlawful assembly, such as the intent to commit a breach of the peace or an unlawful act, and the creation of a tumultuous or violent situation likely to cause public alarm. Additionally, Illinois law also covers related offenses such as rioting and failure to disperse under similar statutes. The penalties for these offenses can vary, but they generally include fines, imprisonment, or both, depending on the severity of the offense and the circumstances surrounding the incident. An attorney can provide specific guidance on how these laws might apply to a particular situation.