A claimant may authorize any individual to represent him or her in regard to a claim under the FECA, unless that individual's service as a representative would violate any applicable provision of law (such as 18 U.S.C. 205 and 208). A Federal employee may act as a representative only:

(a) On behalf of immediate family members, defined as a spouse, children, parents, and siblings of the representative, provided no fee or gratuity is charged; or

(b) While acting as a union representative, defined as any officially sanctioned union official, and no fee or gratuity is charged.