The records referred to in this part and pertaining to the business of the clients serviced by the broker are to be considered confidential, and the broker must not disclose their contents or any information connected with the records to any persons other than those clients, their surety on a particular entry, and the Field Director, Office of International Trade, Regulatory Audit, the special agent in charge, the port director, or other duly accredited officers or agents of the United States, except on subpoena by a court of competent jurisdiction.