China's ADIZ at One Year

Especially because China has sent signals that it might enact another such zone in the South China Sea, this anniversary provides a moment to reflect on the international legality of the East China Sea ADIZ and international rules applicable to it. In general, China’s establishment of an ADIZ is not per se illegal as a matter of international law; however, the requirements China has declared for its East China Sea ADIZ are much broader than recent customary practice by others and China could enforce it in particular ways that would violate international law. Because international law does not yet have much to say about ADIZs, the practices worked out between China, the United States, Japan and others in this case will serve as important baselines for future ADIZs in Asia.

The greatest danger of China’s move is not that it significantly reshapes the core territorial disputes. It is that expanded Chinese military patrols in the air, like its activities at sea, in such close proximity to those of rival players could lead to accidents, provocations, or miscommunications that might easily escalate. So as with maritime activities, for now diplomacy on air activities should focus on creating workable rules of the road and crisis communication mechanisms – and should not be distracted by claims that the ADIZ will substantially affect competing territorial claims. Non-binding codes of conduct would help mitigate dangers in the East China Sea ADIZ. They would also establish a template that could – in the absence of detailed, binding international law on this issue – be used elsewhere should China or other states establish additional zones, especially in other areas encompassing competing territorial claims like the South China Sea.