Blockade
Art. 37. Blockades, in order to be binding, must be effective; that is, they must be maintained by a force sufficient to render hazardous the ingress to or egress from a port.
If the blockading force be driven away by stress of weather and return without delay to its station, the continuity of the blockade is not thereby broken. If the blockading force leave its station voluntarily, except for purposes of the blockade, or is driven away by the enemy, the blockade is abandoned or broken. The abandonment or forced suspension of a blockade requires a new notification of blockade.
Art. 38. Neutral vessels of war must obtain permission to pass the blockade, either from the government of the State whose forces are blockading the port, or from the officer in general or local charge of the blockade. If necessary, these vessels should establish their identity to the satisfaction of the commander of the local blockading force. If military operations or other reasons should so require, permission to enter a blockaded port can be restricted or denied.
Art. 39. The notification of a blockade must be made before neutral vessels can be seized for its violation. This notification may be general, by proclamation, and communicated to the neutral States through diplomatic channels; or it may be local, and announced to the authorities of the blockaded port and the neutral consular officials thereof. A special notification may be made to individual vessels, which is duly indorsed upon their papers as a warning. A notification to a neutral State is a sufficient notice to the citizens or subjects of such State. If it be established that a neutral vessel has knowledge or notification of the blockade from any source, she is subject to seizure upon a violation or attempted violation of the blockade.
The notification of blockade should declare, not only the limits of the blockade, but the exact time of its commencement and the duration of time allowed a vessel to discharge, reload cargo, and leave port.
Art. 40. Vessels appearing before a blockaded port, having sailed before notification, are entitled to special notification by a blockading vessel. They should be boarded by an officer, who should enter upon the ship's log or upon its papers, over his official signature, the name of the notifying vessel, a notice of the fact and extent of the blockade, and of the date and place of the visit. After this notice, an attempt on the part of the vessel to violate the blockade makes her liable to capture.
Art. 41. Should it appear, from the papers of a vessel or otherwise, that the vessel had sailed for the blockaded port after the fact of the blockade had been communicated to the country of her port of departure, or after it had been commonly known at that port, she is liable to capture and detention as a prize. Due regard must be had in this matter to any treaties stipulating otherwise.
Art. 42. A neutral vessel may sail in good faith for a blockaded port, with an alternative destination to be decided upon by information as to the continuance of the blockade obtained at an intermediate port. In such case, she is not allowed to continue her voyage to the blockaded port in alleged quest of information as to the status of the blockade, but must obtain it and decide upon her course before she arrives in suspicious vicinity; and if the blockade has been formally established with due notification, sufficient doubt as to the good faith of the proceeding will subject her to capture.
Art. 43. Neutral vessels found in port at the time of the establishment of a blockade, unless otherwise specially ordered, will be allowed thirty days from the establishment of the blockade, to load their cargoes and depart from such port.