(a) An aerial blockade must be declared by a Belligerent Party and notified to all States.
(b) The declaration must specify the commencement, duration, location, and extent of the aerial blockade and the period in which neutral aircraft may leave the blockaded area.
(c) Whenever feasible, a Notice to Airmen (NOTAM) about the establishment of the aerial blockade ought to be issued by the Blockading Party in accordance with Rule 55.
- This Rule is based on Art. 8 of the 1909 London Declaration, according to which a naval blockade, in order to be binding for neutral navigation must be declared. The same obligation applies to neutral civil aviation in case of an aerial blockade.
- An aerial blockade can either be strategic or local. The declaration of a strategic blockade is reserved to the Blockading Party’s government. A local aerial blockade may be imposed by a competent commander and is of limited extent and duration (e.g., in preparation of a military operation).
- Every aerial blockade must always be notified to all Neutrals. In the case of a strategic aerial blockade, notification must also be given to the enemy government. However, in the case of a local aerial blockade, notification may be addressed to the authorities of the blockaded area.
- Art. 8 of the 1909 London Declaration: “A blockade, in order to be binding, must be declared in accordance with Article 9, and notified in accordance with Articles 11 and 16.”
- The declaration of an aerial blockade must be as specific as possible, in order to enable neutral aviation to avoid the blockaded area or to leave it before enforcement measures take effect. A lack of specificity may render the declaration void. Moreover, all measures taken by the Blockading Party must conform to the particulars of the declaration.
- In principle, the declaration must provide for a period of grace during which neutral aircraft are allowed to leave the blockaded area. There is no absolute rule as to the duration of such a period. However, in most cases 24 hours are considered reasonable. A period of grace must be granted only if, in fact, neutral aircraft are present in the blockaded area.
- Art. 10 of the London Declaration: “If the operations of the blockading Power, or of the naval authorities acting in its name, do not tally with the particulars, which, in accordance with Article 9 (1) and (2), must be inserted in the declaration of blockade, the declaration is void, and a new declaration is necessary in order to make the blockade operative.”
- Art. 9 of the London Declaration: “A declaration of blockade is made either by the blockading Power or by the naval authorities acting in its name. It specifies: … (3) the period within which neutral vessels may come out.”
- The notification of an aerial blockade must be communicated to all States and not merely to those in the region where the aerial blockade has been established. The reason is that, according to Rule 155, an aerial blockade must be enforced against all aircraft regardless of their nationality or origin.
- While Art. 11 of the 1909 London Declaration provides that the notification to Neutrals must be made “by means of a communication addressed to the Governments direct, or to their representatives accredited to it”, today there is no longer a need for such a formal way of making the establishment of an aerial blockade known to the international community.
- Ordinarily, the Blockading Party will fulfil its obligation by making use of the usual channels established for international aviation. Therefore, a NOTAM will in most cases be sufficient as a most effective and timely means of conveying the information necessary. In other words, a notification through diplomatic channels will be necessary in exceptional circumstances only.
- If, notwithstanding the use of the usual channels available for international aviation, the local authorities in the blockaded area cannot be made aware of the establishment of the aerial blockade, the Blockading Party (or the competent commander) will have to inform them separately by whatever means of communication considered adequate.
- Art. 11 of the London Declaration: “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.”