In the absence of appropriate instructions from the Administrator of the Bureau of Security and Consular Affairs, departure-control officers shall not exercise the authority conferred by § 46.2 in the case of any alien who seeks to depart from the United States in the status of a nonimmigrant under section 101(a)(15) (A) or (G) of the Immigration and Nationality Act, or in the status of a nonimmigrant under section 11(3), 11 (4), or 11(5) of the Agreement between the United Nations and the United States of America regarding the Headquarters of the United Nations (61 Stat. 756): Provided, That in cases of extreme urgency, where the national security so requires, a departure-control officer may preliminarily exercise the authority conferred by § 46.2 pending the outcome of consultation with the Administrator, which shall be undertaken immediately. In all cases arising under this section, the decision of the Administrator shall be controlling: Provided, That any decision to prevent the departure of an alien shall be based upon a hearing and record as prescribed in this part.