25 CFR § 11.439 - Witness tampering.
(a) A person commits a misdemeanor if, believing that an official proceeding or investigation is pending or about to be instituted, he or she attempts to induce or otherwise cause a witness or informant to:
(1) Testify or inform falsely; or
(2) Withhold any testimony, information, document or thing; or
(3) Elude legal process summoning him or her to supply evidence; or
(4) Absent himself or herself from any proceeding or investigation to which he or she has been legally summoned.
(b) A person commits a misdemeanor if he or she harms another by any unlawful act in retaliation for anything lawfully done in the capacity of witness or informant.