65 ILCS 5/8-10-8

Any agreement or collusion among bidders or prospective bidders in restraint of freedom of competition by agreement to bid a fixed price, or otherwise, shall render the bids of such bidders void. Each bidder shall accompany his bid with a sworn statement, or otherwise swear or affirm, that he has not been a party to any such agreement. Any disclosure in advance of the opening of bids, of the terms of the bids submitted in response to an advertisement, made or permitted by the purchasing agent shall render the proceedings void and shall require re-advertisement and re-award.