The Board will proceed, upon the petition, responses, and submission of briefs, to determine whether, on the facts before it, the commerce operations of the employer involved are such that the Board would or would not assert jurisdiction over the employer. Such determination will be made by a declaratory order, with like effect as in the case of other orders of the Board, and will be served on the parties. Any party desiring to file a brief must file the brief with the Board in Washington, DC, with a statement that copies are being served simultaneously on the other parties.