D.C. Code § 1-612.10a: Interference prohibited.

An employee shall not directly or indirectly promise to confer on another employee a benefit, such as an appointment, compensation, or promotion, or effect, or suggest to effect on another employee, a reprisal, such as withholding an appointment, reducing compensation, or demoting, for the purpose of interfering with any right that the employee may exercise to contribute, receive, or use leave available under this subchapter.