Is the Establishment of Air Defence Identification Zones Outside National Airspace in Accordance with International Law?

Abstract

Abstract Whereas the right of a state to establish an air defence identification zone (ADIZ) in national airspace falls squarely within its sovereignty, the question whether coastal states may claim such zones outside national airspace remains a matter of controversy. The latter category, referred to as ‘offshore ADIZs’, usually do not amount to sovereignty claims over the open airspace outside national airspace or involve threat or use of force. The right of coastal states to identify aircraft in the open airspace near coastal areas has arguably become part of customary international law. This customary right, however, only extends to ‘passive identification’ by radar detection, radio communication or close visual checks, which thus is only capable of justifying the establishment of offshore ADIZs for this purpose. The identification of aircraft in offshore ADIZs, through either voluntary or passive measures, is nevertheless within the parameters of the obligation of paying due regard to the freedom of overflight. This explains why ‘passive identification’ is ‘permissible’ under customary international law, while ‘voluntary identification’ is at least ‘tolerated’ albeit in the absence of a permissive customary rule.