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 Indiana, the criminal offense of unlawful assembly is addressed under Indiana Code 35-45-1-2, which defines 'Rioting' as when a person knowingly or intentionally engages in tumultuous conduct with at least two other persons that results in substantial damage to property or serious bodily injury to a person or substantially obstructs law enforcement or other governmental functions. Indiana law also includes provisions for related offenses such as disorderly conduct and failure to disperse. Disorderly conduct, under Indiana Code 35-45-1-3, may include fighting or tumultuous conduct, making unreasonable noise, disrupting a lawful assembly, and refusing to leave an area after being asked to do so by law enforcement. Failure to disperse, under Indiana Code 35-45-1-4, involves a person who knowingly or intentionally fails to withdraw from an assembly of five or more persons after being ordered to do so by a law enforcement officer when the assembly is committing or preparing to commit an act of unlawful force or violence. Penalties for these offenses can range from misdemeanors to felonies, depending on the severity of the conduct and the resulting harm or risk created.