(a) Unless required for the disposition of ex parte matters authorized by law, no hearing officer or member of an agency who, in a contested case, is to render a final decision or to make a proposed final decision shall communicate, directly or indirectly, in connection with any issue of fact, with any person or party, or, in connection with any issue of law, with any party or the party's representative, without notice and opportunity for all parties to participate.
(b) Notwithstanding the provisions of subsection (a) of this section, a member of a multimember agency may communicate with other members of the agency regarding a matter pending before the agency, and members of the agency or a hearing officer may receive the aid and advice of members, employees, or agents of the agency if those members, employees, or agents have not received communications prohibited by subsection (a) of this section.
(c) Unless required for the disposition of ex parte matters authorized by law, no party or intervenor in a contested case, no other agency, and no person who has a direct or indirect interest in the outcome of the case, shall communicate, directly or indirectly, in connection with any issue in that case, with a hearing officer or any member of the agency, or with any employee or agent of the agency assigned to assist the hearing officer or members of the agency in such case, without notice and opportunity for all parties to participate in the communication.
(d) The provisions of this section apply from the date the matter pending before the agency becomes a contested case to and including the effective date of the final decision. Except as may be otherwise provided by regulation, each contested case shall be deemed to have commenced on the date designated by the agency for that case, but in no event later than the date of hearing.