Section 31 — Criminal Code: Arrest for breach of peace

Every peace officer who witnesses a breach of the peace and every one who lawfully assists the peace officer is justified in arresting any person whom he finds committing the breach of the peace or who, on reasonable grounds, he believes is about to join in or renew the breach of the peace. Every peace officer is justified in receiving into custody any person who is given into his charge as having been a party to a breach of the peace by one who has, or who on reasonable grounds the peace officer believes has, witnessed the breach of the peace.