5 CFR 731.504: Appellant representatives.

(a) Designation of representative. An appellant may select a representative of his or her choice to assist in the preparation and presentation of an appeal, provided that the appellant submits his or her designation of representative in writing related to the specific appeal.

(b) Federal employee representatives; official time and reimbursement. If the selected representative is a Federal employee, the representative may not perform such representational functions while in a duty status (including while on official time under 5 U.S.C. 7131), nor may the representative claim agency reimbursement for any expenses incurred while performing such representational function.

(c) Disallowance of representative. OPM or the responsible agency may, in its sole and exclusive discretion, disallow an appellant's choice of representative when the representative is an employee of the responsible agency or OPM and the representative's activities would cause a conflict of interest or position.