(1) No person who has served as an officer, attorney, or employee of the department shall appear in an adjudicative proceeding or receive compensation for any services rendered on behalf of any person, firm, corporation, or association in relation to any adjudicative proceeding or application with respect to which such person was directly concerned and in which one personally participated during the period of her or his service or employment.

(2) No person who has served as an officer, attorney, or employee of the department shall appear, except with the permission of the secretary, as an expert witness on behalf of any party, other than the department, in an adjudicative proceeding in which she or he previously took an active part in the matter as a representative of the department.