What does international law say about an attack on Taiwan?

Unlike Russia’s invasion of Ukraine, a future attack by mainland China on Taiwan might be internationally lawful because of Taiwan’s unusual status. But the legal situation is complex and dynamic.

Dr Rowan Nicholson, Lecturer in Law, Flinders University

POLICY PERSPECTIVES #6, October 2023 | DOWNLOAD THIS POLICY PERSPECTIVE | doi.org/10.25957/p8wp-6r05

According to reports, mainland China hopes to be “ready by 2027” to attack Taiwan, though some observers doubt it will actually attack. If it does, policymakers will have many questions: questions about missiles and casualties and how the United States will react. It would be naïve to expect them to focus on international law, which is not likely to have a huge influence on events. Still, it might have some influence. It provides a common language—a legal lingua franca—for states from all continents and with diverse political systems to debate what is right or wrong. It might shape whether some states support one side or the other with funds, sanctions, or even military assistance. We saw that after Russia unlawfully invaded Ukraine in 2022.

To that extent, it matters whether attacking Taiwan is lawful in international law. Probably it is lawful: I will explain why. But as I will also explain, the legal situation is dynamic.

Asking whether an attack is lawful is different from asking whether it is just. International law generally does not care whether force is employed for just reasons. It used to care in the era of “just war” theory. But in that era, each state decided for itself what was just and so in practice force was permissible on any pretext. Since 1945, the law has imposed a ban that is generally agnostic about the justice of the cause: states “shall refrain in their international relations from the threat or use of force against the territorial integrity or political independence of any state” with exceptions where force is in self-defence or authorised by the Security Council. The main aim is not justice but peace, in particular peace among states at the international level.

This means the law does not care, for instance, that Taiwan is a democracy, which is part of the conversation in the United States about whether it is just to support Taiwan. What does interest the law is simply whether force is by one state against another state. This is why it is probably lawful for mainland China to attack Taiwan: they still seem to be parts of a single state.

The legal situation is complex; I will only summarise it. It crystallised in 1949–52 after the civil war between nationalists and communists. At that time, both sides agreed on two points: that China was a single state and that Taiwan, after a period of Japanese rule, was once again part of that state. They disagreed on a third point: the identity of its true government. The nationalist Republic of China now controlled solely Taiwan; the communist People’s Republic of China controlled the mainland. Each claimed to be the true government of the entire state.

This situation—a single state with competing governments—is fairly common in international law. In a typical case, eventually either one government eliminates its rival or else they come to be treated as separate states, including in practice by each other, as with the Koreas. The peculiarity of Taiwan is that, after seven decades, neither of those things has happened.

Taiwan’s position has shifted. As the Republic of China, it occupied China’s seat at the United Nations till 1971, when the seat passed to the People’s Republic of China. In 2007, in contrast, it applied to return to the United Nations not as China but in a separate seat as “Taiwan”. But its application conspicuously avoided the term “state”—unlike, say, Palestine’s application a few years later. More widely, it still uses the name and constitution of the Republic of China. One of the requirements of statehood is independence, which has two elements: effective and formal. Taiwan has a high degree of effective independence, but it seems not to have formally separated from China. That is certainly the view of other states. None has ever recognised it as a separate state—not even its diplomatic allies, which instead still recognise it as representing China.

This implies that if mainland China attacks Taiwan then that is an internal attack, a continuation of the civil war, which is not something the law on the use of force usually regulates.

How is the legal situation dynamic? Taiwan is so close to statehood that arguably the only missing element—all that is needed for the law on the use of force to become applicable—might be to declare independence formally. It has an obvious reason not to do that. Mainland China indicates in its Anti-secession Law that it would respond with “non-peaceful means”. If an attack began anyway Taiwan’s calculation might change, though if its effective independence swiftly came under challenge it might become ineligible for statehood on that ground instead.

Other states might also alter the legal situation. Scholars of statehood and of the use of force speculate that attacking Taiwan might be unlawful even if it is not a separate state, including under provisions of the United Nations Charter requiring the peaceful resolution of disputes. If other states endorse or reject these views, that might strengthen or weaken them.

I observed that international law will not have a huge influence but that it might have some. The legal complexity further diminishes that influence, because a long technical explanation is less compelling than, say, the short simple statement that Russia’s invasion of Ukraine was unlawful. At the same time, the complexity might add to the rhetorical role played by legal language, because actors might be able to defend divergent claims with apparent plausibility.

Dr Rowan Nicholson is a Lecturer in Law at Flinders University

Dr Rowan Nicholson researches in international law with a focus on sovereignty and self-determination. He did his doctorate at Cambridge and has worked on cases in the International Court of Justice. His book Statehood and the State-Like in International Law (Oxford UP 2019) is about how entities acquire international status.

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