Unless required for disposition of an ex parte matter authorized by law, the administrative law judge assigned to a contested case may not communicate, directly or indirectly, in connection with any issue of fact, or question of law, with any person or party or his representative, except on notice and opportunity for all parties to participate. (1973, c. 1331, s. 1; 1985, c. 746, s. 1; 1987, c. 878, s. 11; 2011-398, s. 19.)