“ The Secretary of the Treasury is hereby authorized and empowered to issue such regulations as he may deem necessary to carry out the purposes of this Order. Such regulations may provide for the detention in the United States of any gold coin, gold bullion, or gold certificates sought to be transported beyond the limits of the continental United States, pending an investigation to determine if such coin, bullion, or certificates are held or are to be acquired in violation of the provisions of this Executive Order. ”