29 C.F.R. § 101.25
If it is determined after investigation of the representation petition that further proceedings based thereon are not warranted, the regional director, absent withdrawal of the petition, dismisses it, stating the grounds therefor. If it is determined that the petition does not meet the requirements for processing under the expedited procedure, the regional director advises the petitioner of the determination to process the petition under the procedures described in subpart C of 29 CFR part 102 and the statement of the general course. In either event, the regional director informs all the parties of such action, and such action is final, although the Board may grant an aggrieved party permission to appeal from the regional director's action. Such party must request such review promptly, in writing, and state briefly the grounds relied on. Such party must also immediately serve a copy on the other parties, including the regional director. Neither the request for review by the Board, nor the Board's grant of such review, operates as a stay of the action taken by the regional director, unless specifically so ordered by the Board.
29 C.F.R. §101.25