(1) A person who together in any public or private place commences or attempts to do any of the following acts—
(a) to execute any common purpose with violence, and without lawful authority to use such violence for that purpose;
(b) to execute a common purpose of obstructing or resisting the execution of any legal purpose or authority;
(c) to facilitate, by force or by show of force or numbers, the commission of crime,
commits the offence of rioting.
(2) Persons are not liable of rioting by reason that 2 or more of them suddenly engage in any unlawful fight, unless 2 or more of them fight with a common purpose against some other person or persons.