Chapter I : Blockade in time of war - Art. 11.
Art. 11. A declaration of blockade is notified
(1) To neutral Powers, by the blockading Power, by means of a communication addressed to the Governments direct, or to their representatives accredited to it;
(2) To the local authorities, by the officer commanding the blockading force. The local authorities will, in turn, inform the foreign consular officers at the port or on the coastline under blockade as soon as possible.