29 C.F.R. § 102.9
Any person may file a charge alleging that any person has engaged in or is engaging in any unfair labor practice affecting commerce. The charge may be withdrawn, prior to the hearing, only with the consent of the Regional Director with whom such charge was filed; at the hearing and until the case has been transferred to the Board pursuant to § 102.45 , upon motion, with the consent of the Administrative Law Judge designated to conduct the hearing; and after the case has been transferred to the Board pursuant to § 102.45 , upon motion, with the consent of the Board. Upon withdrawal of any charge, any complaint based thereon will be dismissed by the Regional Director issuing the complaint, the Administrative Law Judge designated to conduct the hearing, or the Board.
29 C.F.R. §102.9