5 C.F.R. § 551.703 – Avenues of review.

(a) Negotiated grievance procedure (NGP) as exclusive administrative remedy. If at any time during the claim period, a claimant was a member of a bargaining unit covered by a collective bargaining agreement that did not specifically exclude matters under the Act from the scope of the NGP, the claimant must use that NGP as the exclusive administrative remedy for all claims under the Act. There is no right to further administrative review by the agency or by OPM. The remaining sections in this subpart (that is, §§ 551.704 through 551.710) do not apply to such employees.
(b) Non-NGP administrative review by agency or OPM. A claimant may file a claim with the agency employing the claimant during the claim period or with OPM, but not both simultaneously, regarding matters arising under the Act if, during the entire claim period, the claimant:
1. (1) Was not a member of a bargaining unit, or
2. (2) Was a member of a bargaining unit not covered by a collective bargaining agreement, or
3. (3) Was a member of a bargaining unit covered by a collective bargaining agreement that specifically excluded matters under the Act from the scope of the NGP.
(c) Judicial review. Nothing in this subpart limits the right of a claimant to bring an action in an appropriate United States court. Filing a claim with an agency or with OPM does not satisfy the statute of limitations governing FLSA claims filed in court. OPM will not decide an FLSA claim that is in litigation.