The underlying objective of criminalization of unlawful assembly is to discourage tumultuous assemblage of persons to preserve public peace. Section 141 of the IPC defines unlawful assembly and section 143 prescribes punishment for the same.
Section 141. 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, 1[the Central or any State Government or Parliament or the Legislature of any State], 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, 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
(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.
To constitute an unlawful assembly, the following ingredients need to be established:
- Five or more persons
- Common object
- Common object specified in the section
Five or more persons
There must be at least five or more persons to constitute an unlawful assembly under section 141. If some of the persons are acquitted or are not brought to trial, making the number less than five, it would make section 141 inapplicable unless there are some other unidentified persons involved.
In Mohan Singh v State of Punjab, wherein five named persons were charged under s302 read with s149, IPC, for committing murder as members of unlawful assembly, and two of them were acquitted by giving them benefit of the doubt, Supreme Court held that the other three could not be convicted as members of the unlawful assembly.
They must have a common object
The word object means a purpose or design. To make it common, the whole unlawful assembly must share it. In other words, the expression common object implies that the object must be shared and possessed by all the members of the assembly. Common object can be gathered from the nature of the assembly, the arms, the manner they used it in, behavior of the members before and after the incident etc.
If four out of five persons possess the common object, it is not an unlawful assembly.
Object must be one of those specified in the section
- Overawing the Central or a State Government or its Officers
To overawe means the creation of apprehension or alarm or fear. A person is said to overawe another when he restrains the other by awe, fear or superior influence.
- Resistance to the execution of legal process
The word resistance implies some overt act. Thus there must be a law that could be executed, its actual execution and resistance to this execution.
- Commission of mischief, criminal trespass or any other offence
This clause is not restricted only to mischief or criminal offence but covers all offences, both against person and property
- Forcible possession and dispossession
- Illegal compulsion
This implies that no one can use criminal force to illegally compel another to do or forbear from any act connected or unconnected with property. There must be some criminal intent coupled with this criminal force. In Mohd Hasnain v Rex, a number of men turned out to remove the pipes laid down by the district board to replace a bridge on the ground that they would obstruct the flow of water, it was held that the object was not unlawful as per this clause.
Section 149. Every member of unlawful assembly guilty of offence committed in prosecution of common object.—If an offence is committed by any member of an unlawful assembly in prosecution of the common object of that assembly, or such as the members of that assembly knew to be likely to be committed in prosecution of that object, every person who, at the time of the committing of that offence, is a member of the same assembly, is guilty of that offence.
Essentials of section 149
- Unlawful assembly
- In prosecution of common object or act that the members knew was likely to be committed in prosecution of common object
- Every person will be liable
The first pre requisite of section 149 is that there must be an unlawful assembly. This means there must be at least five persons or more with a common object as specified in section 141.
Prosecution of common object
Prosecution of common object implies that whatever is necessary to attain the common object is done. Thus this is a very wide term and also includes acts that the members knew were likely to be committed for the prosecution of this common object.
Every person liable
In case the above two essentials are completed, every member of the unlawful assembly will be liable as if the act was done by him alone.
Punishment for unlawful assembly
Section 143 lays down that a member of an unlawful assembly will be punished with imprisonment of a term which may extend to six months and/or fine.
Section 142 lays down that anyone who is aware of the common object and facts that makes an assembly unlawful, joins such an assembly or continues in it, will be said to be a member of that unlawful assembly.
Section 144 lays down that a person armed with deadly weapons , being part of an unlawful assembly will be punished with either imprisonment which may extend to two years or fine or both.
 AIR 1963 SC 174
 AIR 1949 All 351