14 C.F.R. § 305.12
Any person upon whom an investigation subpena is served may, within seven (7) days after such service or at any time prior to the return date thereof, whichever is earlier, file a motion to quash or modify such subpena with the administrative law judge who issued such subpena, or in the event the administrative law judge is not available, with the chief administrative law judge for action by himself or herself or by the DOT decisionmaker. Such motions shall be made in writing in conformity with Rules 3 and 4 of the Rules of Practice (part 302 of this subchapter); shall state with particularity the grounds therefor and the relief sought; shall be accompanied by the evidence relied upon and all such factual matter shall be verified in accordance with the provisions of Rule 4(b) of the aforesaid Rules of Practice. Written memoranda or briefs may be filed with the motions, stating the points and authorities relied upon. No oral argument will be heard on such motions unless the chief administrative law judge, the administrative law judge or the DOT decisionmaker directs otherwise. A subpena will be quashed or modified if the evidence whose production is required is not reasonably relevant to the matter under investigation, or the demand made does not describe with sufficient particularity the information sought, or the subpena is unlawful or unduly burdensome. The filing of a motion to quash or modify an investigation subpena shall stay the return date of such subpena until such motion is granted or denied. The DOT decisionmaker may at any time review, upon his or her own initiative, the ruling of an administrative law judge or the chief administrative law judge denying a motion to quash a subpena. In such cases, the DOT decisionmaker may order that the return date of a subpena which he or she has elected to review be stayed pending DOT action thereon.
14 C.F.R. §305.12