220 ILCS 5/10-103
In all proceedings, investigations or hearings conducted by the Commission, except in the disposition of matters which the Commission is authorized to entertain or dispose of on an ex parte basis, any finding, decision or order made by the Commission shall be based exclusively on the record for decision in the case, which shall include only the transcript of testimony and exhibits together with all papers and requests filed in the proceeding, including, in contested cases, the documents and information described in Section 10-35 of the Illinois Administrative Procedure Act.
The provisions of Section 10-60 of the Illinois Administrative Procedure Act shall apply in full to Commission proceedings, including ratemaking cases, any provision of the Illinois Administrative Procedure Act to the contrary notwithstanding.
The provisions of Section 10-60 shall not apply, however, to communications between Commission employees who are engaged in investigatory, prosecutorial or advocacy functions and other parties to the proceeding, provided that such Commission employees are still prohibited from communicating on an ex parte basis, as designated in Section 10-60, directly or indirectly, with members of the Commission, any administrative law judge in the proceeding, or any Commission employee who is or may reasonably be expected to be involved in the decisional process of the proceeding. Any commissioner, administrative law judge , or other person who is or may reasonably be expected to be involved in the decisional process of a proceeding, who receives, or who makes or knowingly causes to be made, a communication prohibited by this Section or Section 10-60 of the Illinois Administrative Procedure Act as modified by this Section, shall place on the public record of the proceeding (1) any and all such written communications; (2) memoranda stating the substance of any and all such oral communications; and (3) any and all written responses and memoranda stating the substance of any and all oral responses to the materials described in clauses (1) and (2).
The Commission, or any commissioner or administrative law judge presiding over the proceeding, shall in the event of a violation of this Section, take whatever action is necessary to ensure that such violation does not prejudice any party or adversely affect the fairness of the proceedings, including dismissing the affected matter.
220 ILCS 5/10-103