5 U.S.C. § 5537 - Fees for jury and witness service

(a) An employee as defined by section 2105 of this title (except an individual whose pay is disbursed by the Secretary of the Senate or the Chief Administrative Officer of the House of Representatives) or an individual employed by the government of the District of Columbia may not receive fees for service

(b) An official of a court of the United States or the District of Columbia may not receive witness fees for attendance before a court, commissioner, or magistrate judge where he is officiating.

(c) For the purpose of this section, court of the United States has the meaning given it by section 451 of title 28 and includes the District Court of Guam and the District Court of the Virgin Islands.