29 C.F.R. § 825.220 – Protection for employees who request leave or otherwise assert FMLA rights.

(a) The FMLA prohibits interference with an employee's rights under the law, and with legal proceedings or inquiries relating to an employee's rights. More specifically, the law contains the following employee protections:
1. (1) An employer is prohibited from interfering with, restraining, or denying the exercise of (or attempts to exercise) any rights provided by the Act.
2. (2) An employer is prohibited from discharging or in any other way discriminating against any person (whether or not an employee) for opposing or complaining about any unlawful practice under the Act.
3. (3) All persons (whether or not employers) are prohibited from discharging or in any other way discriminating against any person (whether or not an employee) because that person has—
  1. (i) Filed any charge, or has instituted (or caused to be instituted) any proceeding under or related to this Act;
  2. (ii) Given, or is about to give, any information in connection with an inquiry or proceeding relating to a right under this Act;
  3. (iii) Testified, or is about to testify, in any inquiry or proceeding relating to a right under this Act.
(b) Any violations of the Act or of these regulations constitute interfering with, restraining, or denying the exercise of rights provided by the Act. An employer may be liable for compensation and benefits lost by reason of the violation, for other actual monetary losses sustained as a direct result of the violation, and for appropriate equitable or other relief, including employment, reinstatement, promotion, or any other relief tailored to the harm suffered. See § 825.400(c). Interfering with the exercise of an employee's rights would include, for example, not only refusing to authorize FMLA leave, but discouraging an employee from using such leave. It would also include manipulation by a covered employer to avoid responsibilities under FMLA, for example:
1. (1) Transferring employees from one worksite to another for the purpose of reducing worksites, or to keep worksites, below the 50-employee threshold for employee eligibility under the Act;
2. (2) Changing the essential functions of the job in order to preclude the taking of leave;
3. (3) Reducing hours available to work in order to avoid employee eligibility.
(c) The Act's prohibition against interference prohibits an employer from discriminating or retaliating against an employee or prospective employee for having exercised or attempted to exercise FMLA rights. For example, if an employee on leave without pay would otherwise be entitled to full benefits (other than health benefits), the same benefits would be required to be provided to an employee on unpaid FMLA leave. By the same token, employers cannot use the taking of FMLA leave as a negative factor in employment actions, such as hiring, promotions or disciplinary actions; nor can FMLA leave be counted under no fault attendance policies. See § 825.215.
(d) Employees cannot waive, nor may employers induce employees to waive, their prospective rights under FMLA. For example, employees (or their collective bargaining representatives) cannot trade off the right to take FMLA leave against some other benefit offered by the employer. This does not prevent the settlement or release of FMLA claims by employees based on past employer conduct without the approval of the Department of Labor or a court. Nor does it prevent an employee's voluntary and uncoerced acceptance (not as a condition of employment) of a light duty assignment while recovering from a serious health condition. See § 825.702(d). An employee's acceptance of such light duty assignment does not constitute a waiver of the employee's prospective rights, including the right to be restored to the same position the employee held at the time the employee's FMLA leave commenced or to an equivalent position. The employee's right to restoration, however, ceases at the end of the applicable 12-month FMLA leave year.
(e) Individuals, and not merely employees, are protected from retaliation for opposing (e.g., filing a complaint about) any practice which is unlawful under the Act. They are similarly protected if they oppose any practice which they reasonably believe to be a violation of the Act or regulations.