40 C.F.R. § 7.100
Intimidation and retaliation prohibited
No applicant, recipient, nor other person shall intimidate, threaten, coerce, or discriminate against any individual or group, either:
(a) For the purpose of interfering with any right or privilege guaranteed by the Acts or this part, or
(b) Because the individual has filed a complaint or has testified, assisted or participated in any way in an investigation, proceeding or hearing under this part, or has opposed any practice made unlawful by this regulation.