29 CFR §18.21

1. (a)In general. A party may appear and participate in the proceeding in person or through a representative.
2. (b)Waiver of participation. By filing notice with the judge, a party may waive the right to participate in the hearing or the entire proceeding. When all parties waive the right to participate in the hearing, the judge may issue a decision and order based on the pleadings, evidence, and briefs.
3. (c)Failure to appear. When a party has not waived the right to participate in a hearing, conference or proceeding but fails to appear at a scheduled hearing or conference, the judge may, after notice and an opportunity to be heard, dismiss the proceeding or enter a decision and order without further proceedings if the party fails to establish good cause for its failure to appear.