The Memo: Chinese spy balloon raises international law concerns

Cait Evans – 20 February 2023

The now infamous case of the Chinese spy balloon has caused quite the stir amongst politicians and diplomats across the globe. It has aggravated already thinning US-China relations, with the Pentagon calling it a ‘clear violation of international law’, whilst China maintains it was a civilian meteorological ship that had drifted off course. But what does international law actually tell us about balloon spying?

Spying balloons can be traced all the way back to the Napoleonic era, and were principally used for reconnaissance in wartime, but they were also used to carry small bombs. After the First World War, their use significantly diminished, and these days they're even more scarce given the development of drones and satellites. But for some nations, they have remained attractive for spying because they are tricky to detect on radar and can be easily disguised.

Unlike the Napoleonic era, entering foreign airspace these days without permission violates international law. The law on airspace is governed by a range of treaties and conventions like the Chicago Convention of 1944. which contains the principle that countries have complete and exclusive sovereignty over their own airspace. The problem is there is no international treaty that defines a limit to a nation’s airspace, so it is not entirely clear to what extent a foreign balloon would be considered entering a country’s air territory.

We get a better understanding by looking at what isn’t. It’s clear in principle that countries cannot have sovereignty over outer space. So, looking at where space begins, and earth’s atmosphere ends, is a good starting point.

Whilst there is no definition in law of where outer space begins, NASA and the US consider space starting at around 262,000ft, but in the international community it is a little higher. The Fédération Aéronautique Internationale (FAI) defines the boundary between outer space and Earth’s atmosphere at around 330,000ft, known as the Karman line. This number is set way above the altitude of where commercial airplanes can reach. It is alleged that the balloon was flying at an altitude of 60,000ft, so it clearly falls below any understanding of outer space.

Moreover, there are international legal frameworks which allow governments to seek permission to enter a foreign airspace and the USA has its own, known as the ‘air defense identification zone’ (ADIZ). This requires any aircraft flying into American airspace to identify themselves. So given the fact China has clearly entered US airspace and not asked for permission, it is a clear violation of international law, and the US were within their rights to shoot down the balloon.

The balloon saga is not the first diplomatic dispute between the US & China. China have long contested the presence of US warships in the Taiwan Strait, which China claims as its own territory, so there is little sign of tensions deescalating anytime soon. Keep a close eye on how both sides respond over the coming months, as their actions will determine how their relationship develops and if we can expect any more provocations which will further challenge the boundaries of international law.