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 § 215.2 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 § 215.2 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.