5 C.F.R. § 2422.24

(a) Filing challenges. A party or the FLRA may, for good cause, challenge the eligibility of any person to participate in the election.

(b) Challenged ballot procedure. An individual whose eligibility to vote is in dispute will be given the opportunity to vote a challenged ballot. If the parties and the FLRA are unable to resolve the challenged ballot(s) before the tally of ballots, then the FLRA will impound and preserve the unresolved challenged ballot(s) until the FLRA makes a determination, if necessary.