'Symbolic politics'

DW: Can you briefly explain how airspace sovereignty is defined by international law and the rights and responsibilities associated with it?

Stefan Talmon: Each state has air sovereignty over its territory, encompassing its land area as well as the airspace over the territorial sea, which extends up to 12 nautical miles from the coast. The countries may impose regulations over the aircraft passing through this area.

The governments can also monitor the flights or prohibit airlines from entering this airspace. Basically, it's like crossing a land border, except that in this case it is a border in the air.

Which rules apply for international air traffic in these air zones?

Due to the air sovereignty of nation-states, their governments may determine who flies in their airspace and who doesn't.

The countries have given international airlines certain flyover and landing rights in their territories by ratifying the Chicago Convention on International Civil Aviation and the International Air Services Transit Agreement of 1944. With these treaties in place, international air traffic has been largely regulated since then.

So why are the air defense identification zones (ADIZ) recently established by China and South Korea so controversial?

These zones are unrelated to a state's air sovereignty. One can see that the zones extend to areas far beyond the designated territorial waters and over the high seas, where no state exercises control of the skies.

All countries have equal rights to use this airspace according to the principle of "the freedom of the high seas." There is neither a need for any special permit to fly here nor can any state restrict this right unilaterally by declaring special zones.

The air defense zone is not about restricting flyover rights, but about preventing potential attacks on national territory by requesting information. This is why all states ask all airlines flying into such a zone to identify themselves, submit their flight plans, and name their destination.

According to international law, airlines are not obliged to comply as long as they don't plan to enter that country's airspace. However, most of them do for security reasons.

So the air defense zone is not relevant under international law?

There are no provisions in international law designed to regulate the establishment of such zones. In such cases, a basic legal principle is applied, according to which, the concept of sovereignty allows states to do anything which is not explicitly forbidden by international law.

Legal restrictions would only apply if a state claimed sovereignty, sovereign rights or jurisdiction over the high seas. The simple action of requesting airlines to identify themselves and provide information cannot be regarded as a claim to ADIZ's air space.

How significant are China's and South Korea's moves to establish and enlarge their respective air defense zones?

The main purpose of these zones is not air defense, but rather symbolic politics. These countries want to underscore their territorial claims to certain islands located within the ADIZ. But these claims cannot be justified under international law by simply declaring an ADIZ. These countries are rather sending the political signal: "We are entitled to these islands."

Stefan Talmon is a professor for international law at the University of Bonn.

The interview was conducted by Rodion Ebbighausen.