5 CFR 2422.24 - What are challenged ballots?
(a) Filing challenges. A party or the Regional Director 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 Region are unable to resolve the challenged ballot(s) before the tally of ballots, the Region will impound and preserve the unresolved challenged ballot(s) until the Regional Director makes a determination, if necessary.