The crime of mob action in Illinois is defined by 720 ILCS 5/25-1 as follows.
(a) A person commits mob action when he or she engages in any of the following:
(1) the knowing or reckless use of force or violence disturbing the public peace by 2 or more persons acting together and without authority of law;
(2) the knowing assembly of 2 or more persons with the intent to commit or facilitate the commission of a felony or misdemeanor; or
(3) the knowing assembly of 2 or more persons, without authority of law, for the purpose of doing violence to the person or property of anyone supposed to have been guilty of a violation of the law, or for the purpose of exercising correctional powers or regulative powers over any person by violence.
Mob action in violation of paragraph (1) is a Class 4 felony, punishable by 1-3 years in an Illinois state prison.
Mob action in violation of paragraphs (2) and (3) is a Class C misdemeanor, which can result in up to 30 days in the county jail.
A participant in a mob action that by violence inflicts injury to the person or property of another commits a Class 4 felony, which is punishable by 1-3 years in prison.
A participant in a mob action who does not withdraw when commanded to do so by a peace officer commits a Class A misdemeanor, which can result in up to a year in jail.
It is common for those charged with mob action in Illinois to also face charges such as aggravated battery, as prosecutors will often charge mob action in cases where multiple people are accused of jointly attacking another person.
Mob action and charges that tend to accompany it in Illinois are serious matters that can result in a lengthy term of incarceration. For that reason any person facing a mob action charge should consult with an attorney at once.