25 ILCS 5/13
The sergeant-at-arms of the senate and his assistants, and the doorkeeper of the house of representatives and his assistants, shall serve such process and execute such orders as may be enjoined upon them by their respective houses, shall maintain order among spectators admitted into the rooms in which the respective houses hold their sessions, and take proper measures to prevent interruption of either house, and may arrest, with or without warrant, any person committing any offense created by this act, or by any law for the protection of the state house or any of its grounds or appurtenances, or guilty of any breach of the peace in or about the state house or public grounds connected therewith, and convey any such offender before the proper court for trial; and for such purpose they shall have the same authority as is granted to sheriffs.
25 ILCS 5/13