36 CFR §1150.13

1. (a)By petitioning the judge, any person may be permitted to participate in the proceedings when he/she claims an interest in the proceedings and may contribute materially to their proper disposition. A complainant shall be permitted to participate in the proceeding when he/she petitions the judge.
2. (b)The judge may, in his/her discretion, determine the extent of participation of petitioners, including as an intervening party or participant. The judge may, in his/her discretion, limit participation to submitting documents and briefs, or permit the introduction of evidence and questioning of witnesses.