29 CFR §102.105

Whenever both an unfair labor practice charge and a representation case relating to the same employer are contemporaneously on file in a Regional Office of the Board, and the General Counsel entertains doubt whether the Board would assert jurisdiction over the employer involved, the General Counsel may file a petition with the Board for a declaratory order disposing of the jurisdictional issue in the case. Such petition may be withdrawn at any time prior to the issuance of the Board's order.