(a) Compulsory attendance of witnesses and production of documents. The Commission and its Judges are authorized to issue subpoenas, on their own motion or on the oral or written application of a party, requiring the attendance of witnesses and the production of documents or physical evidence. A subpoena may be served by any person who is at least 18 years of age. A subpoena may also be served by registered or certified mail, return receipt requested, but, in such case, any risk of delivery is on the serving party. A copy of the subpoena bearing a certificate of service shall be filed with the Commission or the Judge.

(b) Fees payable to witnesses. Subpoenaed witnesses shall be paid the same fees and mileage as are paid in the district courts of the United States. The witness fees and mileage shall be paid by the party at whose request the witness appears, or by the Commission if a witness is subpoenaed on the motion of the Commission or a Judge. This paragraph does not apply to Government employees who are called as witnesses by the Government.

(c) Motions to revoke or modify subpoenas. Any person served with a subpoena may move within 5 days of service or at the hearing, whichever is sooner, to revoke or modify the subpoena. The Commission or the Judge, as appropriate, shall revoke or modify the subpoena if it seeks information outside the proper scope of discovery as set forth in § 2700.56(b); or if it does not describe with sufficient particularity the evidence required to be produced; or if for any other reason it is found to be invalid or unreasonable. The Commission or the Judge shall set forth a concise statement of the grounds for such ruling.

(d) Availability of transcript. Persons compelled to submit evidence at a public proceeding are entitled to obtain, on payment of prescribed costs, a transcript of that part of the proceeding that sets forth their testimony or refers to their production of evidence.

(e) Failure to comply. Upon the failure of any person to comply with an order to testify or with a subpoena issued by the Commission or the Judge, the Judge or the Commission's General Counsel, at the request of the Judge or at the direction of the Commission, may undertake to initiate proceedings in the appropriate district court of the United States for the enforcement of the subpoena.