39 CFR 960.16: Comments by other parties.

Any party to a proceeding other than the applicant and Postal Service may file comments on an application within 30 days after it is served or on an answer within 15 days after it is served. A commenting party may not participate further in proceedings on the application unless the adjudicative officer determines that the public interest requires such participation in order to permit full exploration of matters raised in the comments.