The term Unlawful assembly means a group of people ( the number varies from country to country)with the mutual intent of deliberate disturbance of the peace.In English law, the term unlawful assembly is used 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 Bangladesh, the assembly should consist of more than five persons. The object of the assembly should be one of the following five objects –

(a)To overawe by criminal force, or show of criminal force, the Central or any State Government or Parliament or the Legislature of any State, or public servant in the exercise of the lawful power of such public servant; or

(b)To resist the execution of any law, or of any legal process; or

(c) To commit any mischief or criminal trespass, or other offence; or

(d) By means of criminal force, or show of criminal force, to any person, to take or obtain possession of any property, or to deprive any person of the enjoyment of a right of way, or of the use of water or other incorporeal right of which he is in possession or enjoyment, or to enforce any right or supposed right; or

(e) By means of criminal force, or show of criminal force, to compel any person to do what he is not legally bound to do, or to omit to do what he is legally entitled to do. Such object was common to all the members assembled. The accused joined or continued the said assembly and he did so being aware of the above facts. Whoever, being aware of the facts, which render any assembly an unlawful assembly, intentionally joins that assembly, or continues in it, is said to be a member of an unlawful assembly.

It is remarkable that an assembly, which was not unlawful when it assembled, might subsequently become an unlawful assembly.

An assembly of five or more persons is designated an "unlawful assembly," if the common object of the persons composing that assembly is—

First.—to overawe by criminal force, or show of criminal force, Government or Legislature, or any public servant in the exercise of the lawful power of such public servant; or

Second.—to resist the execution of any law, or of any legal process; or

Third.—to commit any mischief or criminal trespass, or other offence; or

Fourth.—by means of criminal force, of show of criminal force, to any person to take or obtain possession of any property, or to deprive any person of the enjoyment of a right of way, or of the use of water or other incorporeal right of which he is in possession or enjoyment, or to enforce any right or supposed right: or

Fifth.—By means of criminal force, or show of criminal force, to compel any person to do what he is not legally bound to do, or to omit to do what he is legally entitled to do.

Explanation.—An assembly which was not unlawful when it assembled, may subsequently become an unlawful assembly. [Section 141 of the Penal Code, 1860]

Before applying section 149 of the Penal Code the Court Must have indubitable evidence that the members of the unlawful assembly constituted the statutory number of five, though some of them might not have been named, or identified, or brought to trail. [Rafiqul Islam vs. The State 13 BLD (AD)117]