27 C.F.R. § 71.83
Any evidence which would be admissible under the rules of evidence governing proceedings in matters not involving trial by jury in the Courts of the United States, shall be admissible and controlling as far as possible: Provided, That the administrative law judge may relax such rules in any hearing when in his judgment such relaxation would not impair the rights of either party and would more speedily conclude the hearing, or would better serve the ends of justice. Except as provided in §71.81, the proponent of an order shall have the burden of proof. Every party shall have the right to present his case or defense by oral or documentary evidence, depositions, duly authenticated copies of records and documents, to submit rebuttal evidence, and to conduct such reasonable cross-examination as may be required for a full and true disclosure of the facts. The administrative law judge shall have the right in his discretion to limit the number of witnesses whose testimony may be merely cumulative and shall, as a matter of policy, not only exclude irrelevant, immaterial, or unduly repetitious evidence but shall also limit the cross-examination of witnesses to reasonable bounds so as not to unnecessarily prolong the hearing and unduly burden the record. Material and relevant evidence shall not be excluded, because it is not the best evidence, unless its authenticity is challenged, in which case reasonable time shall be given to establish its authenticity. When portions only of a document are to be relied upon, the offering party shall prepare the pertinent excerpts, adequately identified, and shall supply copies of such excerpts, together with a statement indicating the purpose for which such materials will be offered, to the administrative law judge and to the other parties. Only the excerpts, so prepared and submitted, shall be received in the record. However, the whole of the original document should be made available for examination and for use by opposing counsel for purposes of cross-examination. Compilations, charts, summaries of data and photostatic copies of documents may be admitted in evidence if the proceedings will thereby be expedited, and if the material upon which they are based is available for examination by the parties. Objections to the evidence shall be in short form, stating the grounds relied upon. The transcript shall not include argument or debate on objections, except as ordered by the administrative law judge, but shall include the rulings thereon.
27 C.F.R. § 71.83