Unlawful assembly is a legal term to describe a group of people with the mutual intent of deliberate disturbance of the peace. If the group are about to start the act of disturbance, it is termed a rout; if the disturbance is commenced, it is then termed a riot. In Britain, the offence was abolished in 1986.
By the 19th century, unlawful assembly was the term used in English law for an assembly of three or more persons with intent to commit a crime by force, or to carry out a common purpose (whether lawful or unlawful), in such a manner or in such circumstances as would in the opinion of firm and rational men endanger the public peace or create fear of immediate danger to the tranquillity of the neighbourhood. In the Year Book of the third year of Henry VII's reign assemblies were referred to as not punishable unless in terrorem populi domini regis. It was suggested[a] that legislation first became necessary at a time when it was usual for those landed proprietors who were on bad terms with one another to go to market at the head of bands of armed retainers.[b] An assembly, otherwise lawful, was not made unlawful if those who take part in it know beforehand that there will probably be organized opposition to it, and that it may cause a breach of the peace.[c] All persons may, and must if called upon to do so, assist in dispersing an unlawful assembly.[d] An assembly which was lawful could not be rendered unlawful by proclamation unless the proclamation was one authorized by statute.[e] Meetings for training or drilling, or military movements, were unlawful assemblies unless held under lawful authority from the Crown, the Lord Lieutenant, or two justices of the peace.[f]
An unlawful assembly which has made a motion towards its common purpose was termed a rout, and if the unlawful assembly should proceed to carry out its purpose, e.g. begin to demolish a particular enclosure, it became a riot. All three offences were misdemeanours in English law, punishable by fine and imprisonment. The offence was abolished by the Public Order Act 1986.
The common law as to unlawful assembly extended to Ireland, subject to special legislation. The law of Scotland included unlawful assembly under the same head as rioting.
Section 409 is a section of the Code of Criminal Procedure, which prohibits assembly of five or more persons, holding of public meetings, and carrying of firearms and can be invoked for up to two months. It also gives the magistracy the power to issue order absolute at once in urgent cases of nuisance or apprehended danger. With the introduction of Dhaka Metropolitan Police (DMP) in 1976, Section 144 has ceased to operate in the metropolitan jurisdiction in Bangladesh.
Under Part II of the Canadian Criminal Code (Offences Against Public Order), Unlawful Assemblies and Riots is when the assembly of three or more persons who cause fear and on reasonable grounds disturb peace in the neighborhood against the law.
The Public Order Ordinance (chapter 245 of the laws of Hong Kong) defines "unlawful assembly" (§18) as an assembly of three or more persons conducting themselves in a "disorderly, intimidating, insulting or provocative manner intended or likely to cause a person reasonably to fear that the persons so assembled will conduct a breach of the peace or will by such conduct provoke other persons to commit a breach of the peace". Persons taking part in unlawful assemblies can be punished with up to five years imprisonment (if indicted) or a level 2 fine (HK$5000) and imprisonment for two years (on summary conviction). 
Section 144 of the Criminal Procedure Code (CrPC) of 1973, empowers a magistrate to prohibit an assembly of more than ten people in an area. According to sections 141-149 of the Indian Penal Code (IPC), the maximum punishment for engaging in rioting is rigorous imprisonment for 3 years and/or fine. Every member of an unlawful assembly can be held responsible for a crime committed by the group. Obstructing an officer trying to disperse an unlawful assembly may attract further punishment.
The section was used for the first time in 1861 by the British Raj, and thereafter became an important tool to stop all nationalist protests during the Indian independence movement, and its use in independent India remains controversial as little has changed. It is often used to prevent protests or demonstrations, even the law doesn't use the terms, though it does mention "riot". The issue was further highlighted following the protests in the aftermath of the 2012 Delhi gang rape. When in December, 2012, a special executive magistrate imposed prohibitory orders around India Gate, a popular location for public protests, under the section for up to six months. In January 2013, the Delhi High Court issued a notice to Delhi Police in this regard as it found the orders contrary to the fundamental rights of citizens.
- Criminal Code Commission, 1879
- Statute of Northampton, 1328, 2 Edw. III. c. 3
- Beatty v. Gillbanks, 1882, 9 Q. B. D. 308
- Redford v. Birley, 1822, 1 St. Tr. n.s. 1215; R. v. Pinney, 1831, 3 St. Tr. n.s. 11
- R. v. Fursey, 1833, 3 St. Tr. n.s. 543, 567; R. v. O'Connell, 1831, 2 St. Tr. n.s. 629, 656; see also the Prevention of Crimes [Ireland] Act 1887
- Unlawful Drilling Act 1820, s. 11
- One or more of the preceding sentences incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). "Assembly, Unlawful". Encyclopædia Britannica 1 (11th ed.). Cambridge University Press.
- Bangladesh Criminal Justice Based on the Country Studies Series by Federal Research Division of the Library of Congress
- Code of Criminal Procedure: Issue Paper on Bangladesh State Protection Immigration and Refugee Board of Canada. Retrieved: July 01, 2007.
- Pakistan Code of Criminal Procedure, Section 144
- Role of Criminal Law in the protection of the Environment:Bangladesh context Asian Crime Prevention Foundation. Retrieved: July 01, 2007.
- Dhaka siege: Some unanswered questions The New Age. Retrieved: July 01, 2007.
- "Criminal Procedure Ordinance Levels of Fines for offences". Retrieved 19 January 2015.
- "Section 144 in The Code Of Criminal Procedure, 1973". Retrieved 2014-03-01.
- "Dissecting Section 144: Have prohibitory orders become a tool used in daily police work?". Economic Times. Retrieved 2014-03-01.
- "HC issues notice to police on Section 144 of CrPc at India Gate". The Hindu, Business Line. January 8, 2013. Retrieved 2014-03-01.