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5 U.S. Code § 6338 - Prohibition of coercion

An employee may not directly or indirectly intimidate, threaten, or coerce, or attempt to intimidate, threaten, or coerce, any other employee for the purpose of interfering with any right which such employee may have with respect to contributing, receiving, or using annual leave under this subchapter.
For the purpose of subsection (a), the term “intimidate, threaten, or coerce” includes promising to confer or conferring any benefit (such as an appointment, promotion, or compensation), or effecting or threatening to effect any reprisal (such as deprivation of appointment, promotion, or compensation).