Editor’s note:

One of the most complicated issues in contemporary international relations is the status of the self-governing island of Taiwan and its government in Taipei, formally called the government of the Republic of China (ROC). Is Taiwan a sovereign state? What is the legal relationship between the ROC and the People’s Republic of China (PRC)? How much of US support for Taiwan is grounded in law and how much in policy? Does international law recognize Taiwan’s right of self-defense or the right of its friends to come to its aid?

During the 2024-2025 academic year, the U.S.-Asia Law Institute (USALI) hosted a series of speakers to address these and related questions from different perspectives. In this Nov. 7, 2024 talk, Peter Dutton, a senior research scholar at the Paul Tsai China Center at Yale Law School, explains the US view that title to the territory of Taiwan and the Penghu Islands did not revert to China after World War II, and remains “undetermined” in international law. Dutton also argues that Taiwan is a “declaratory state,” one that fulfills a long-standing international test of statehood regardless of how many or few other states formally recognize Taiwan.

The following excerpts from that talk have been edited lightly for clarity and brevity. A full recording of the program can be found here. The discussion was moderated by Katherine Wilhelm, executive director of the US-Asia Law Institute.

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By Peter Dutton

Today I am focused on the legal status of the island of Taiwan itself. Here is where the People’s Republic of China (PRC) begins the conversation: there's one China in the world, Taiwan is an inalienable part of China, and the People's Republic of China is the sole legal government representing the whole of China. This is a claim of sovereignty over the territory of Taiwan and the right to govern that territory.

There was a time when China had undisputed sovereignty over Taiwan. The Qing dynasty was the undisputed sovereign of the territory of Taiwan and the Penghu Islands. [But in 1894-1895 China and Japan fought a war, and in April 1895, they signed] the Treaty of Shimonoseki by which China ceded the territory of Taiwan and the Penghu Islands to Japan. ... [After the start of World War II,] the Chinese government purported to abrogate all of the treaties that it had signed with Japan.

In 1943, as the war raged on, the British, the Americans, and the Chinese met in Cairo to lay out the conduct of the rest of the war. The only thing that they were able to agree on was that Taiwan and the Penghu Islands would be returned to China upon the defeat of Japan.

This was followed by a meeting at Potsdam in 1945, where Britain, the United States, and the Soviet Union agreed to implement the Cairo agreement. When Japan surrendered and signed a surrender agreement, it agreed to abide by the provisions of the Potsdam accord. Subsequently, the government of the Republic of China sent representatives to Taipei to accept the Japanese surrender. This happened in late October 1945.

It was the policy of the Truman administration to complete the agreement that Roosevelt had made at Cairo, and to hand over Taiwan and the Penghu Islands to China in the formal peace treaty that would follow the conflict. That was Truman’s policy until North Korea attacked South Korea. At that point, Truman believed that Stalin was attempting to take advantage of Allied weakness to expand communist control across Eurasia. He changed the policy overnight. He [decided that] the determination of Taiwan’s future status must await the restoration of security in the Pacific.

The next action was the San Francisco Peace Treaty [in 1951]. Even though the conflict ended with the surrender agreement in 1945, a peace treaty ends the formal state of hostilities. Japan was required to renounce its sovereignty over Taiwan and the Penghu Islands, but no other party was assigned sovereignty.

Japan was required to renounce its sovereignty over Taiwan and the Penghu Islands, but no other party was assigned sovereignty. ... The status of Taiwan as a matter of international law is undetermined.

The Republic of China and Japan signed a second peace treaty [in 1952], because there was no Chinese representative at the San Francisco Peace Treaty. There was no claim of a resumption of sovereignty [by China] over Taiwan and the Penghu Islands in that [second] treaty.

Fast forward through almost 20 years of Cold War. US President Richard Nixon went to China in February 1972, and came to political agreements with PRC Premier Zhou Enlai. ... It was Nixon's policy that Taiwan was part of China, but it was not the US government's policy. In fact, the Shanghai Communiqué [of 1972] was a very ambiguous, poorly worded, difficult to understand document. ...

My assessment, looking at each of the different historical events, and looking at each of the Chinese arguments about the status of Taiwan, is that the best legal answer is that the status of Taiwan remains undetermined as an outcome of World War II. It's perhaps tainted with unfairness, it's perhaps tainted with power politics, but the law is what the law is, and fairness is something perhaps separate. The status of Taiwan, as a matter of international law, is undetermined, and Taiwan is best described as what I would call a declarative state.

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Wilhelm: Briefly, what does sovereignty mean and how is it established?

Dutton: Sovereignty means a lot of things, but fundamentally, it's the right to govern territory and to be accepted as a member of the international community. There are two tests [of sovereignty] under international law that are somewhat in tension with each other. There's a lot of overlap between them, but there's a tension between them.

The first and longest-standing test is called the declarative test of sovereignty.

There is a government;
There is are people that it governs;
There is territory over which it governs;
And it is capable of engaging in international relations.

Then it's sovereign and should be given all of the rights, privileges, and obligations of sovereignty.

There's a separate test, however, called the constitutive test. The constitutive test takes the first four elements and then adds the element of recognition. It says: “Well, you may have all of the elements of declarative sovereignty, but unless other states recognize you, then you're not actually a sovereign equal to the other states.”

Wilhelm: Why does it matter whether Taiwan is a declared state or a constitutive state? Is this just an academic debate?

Dutton: I don't think so and I don't think the Taiwanese think so. The first and most important thing is that the UN is a constitutive system. In order to be a member of the United Nations, you have to be accepted as [a sovereign]. We have a Security Council where five permanent members [the P5] can determine whether a state can be a sovereign. ... China has actively prevented Taiwan from ... moving from its status as a declarative state to a constitutive state – a full sovereign state and member of the international system. Unless you're accepted first by the P5 and second by a majority of the General Assembly ... you can't become a fully recognized participant in the United Nations. [You can’t take] advantage of all of the privileges and rights that come with that, including the UN Charter’s collective self-defense components.

Wilhelm: A declarative state is a second-class state. It's protected by customary international law, but not by the UN Charter. So it has fewer rights?

Dutton: I think that's a good way of putting it. There are, in a sense, two tiers of states. You have full states that are fully accepted as having constituted sovereignty. These states can be members of the United Nations and take advantage of all aspects of the international system. And there are, and have always been historically, other polities that are not fully recognized and accepted among the community of states. In modern times, we have for instance Kosovo and Palestine. ... Taiwan. is [also] an example of a declarative state. I'm using “Taiwan” here to mean the government on Taiwan, which I recognize is more than just the geographic island.

There are, in a sense, two tiers of states. You have full states that are fully accepted as having constituted sovereignty. And there are, and have always been historically, other polities that are not fully recognized and accepted among the community of states.

Wilhelm: If you're not deemed to be a state, you can't participate at the UN, you can't participate in discussions about international law or in international bodies that are under the UN, unless you're allowed to come in as an observer. US arms sales to Taiwan would be deemed illegal under international law if Taiwan is not a state of some kind. And then, as you said, no right to collective defense. Right? These are concrete consequences.

Dutton: I might not go quite so far as how you put it there, because I do think Taiwan actively participates in the development of international law in various ways. For instance, Taiwan participates in the development of human rights. You might also think of the ways in which it attempts to influence the development of international commercial and business law. What it is precluded from is the formal influences. The Taiwanese cannot have a judge on the International Court of Justice; they cannot participate as members in the international Seabed Authority.

Wilhelm: So if we ask “is Taiwan a state?” there is not a simple yes-no answer?

Dutton: I avoided that question so far. Primarily, today's presentation really is about what's the status of the territory. I did take it one step further and say that I think it's the government of Taiwan is a declarative state. But fundamentally, I think you have a lot of different permutations, in part because there are really three different types of territory the Republic of China on Taiwan governs. There's the territory with an undetermined sovereign status, that's [the island of] Taiwan and the Penghu islands. Second, you have Jinmen and Mazu, territory that I don't think anyone disputes is actually Chinese territory. I would include Dongsha in that as well. The Pratus Reef, I think, like Jinmen and Mazu, has always been Chinese, at least since the late Qing dynasty. Then, Taiwan occupies and governs Taiping Island in the Spratlys, which is fully contested territory. So you have at least three different types of territory that Taiwan actually governs, which is in part why there are so many possible permutations that one could come up with about “what is the government on Taiwan.”

Respect for sovereignty is fundamentally about stability in the international system, preventing frequent changes of boundaries, and preventing wars caused by frequent changes of boundaries.
Wilhelm: Maybe one way to get a little bit more clarity on what you're saying about Taiwan’s status would be to contrast it with another case. You've mentioned Kosovo, Palestine, and other contested states.

Dutton: I think each of the three declarative states that I discussed – Kosovo, Palestine, and Taiwan – has its own unique set of historical circumstances that led to where it is today. ... Why is Kurdistan not a separate sovereign? Why is Somaliland not a separate sovereign? ... There's a tension between self-determination and respect in international law. Respect for sovereignty is fundamentally about stability in the international system, preventing frequent changes of boundaries, and preventing wars caused by frequent changes of boundaries. But self-determination comes out of human rights law and the idea of the right or the justice behind self-determination of people: if they want to be separate from another government, then they should be separate from another government. Self-determination was given preference during the exiting out of global colonialism, where peoples that had been colonized were given an opportunity to exercise self-determination. ... Today, since we're largely beyond the period of colonialism, the law has shifted to give more preference to sovereignty than self-determination.

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Audience question: One can argue that for well over half a century, Taiwan was a Japanese colony. At the end of the war, its people should have been granted self-determination rights.

Dutton: The people on Taiwan have actually been able to exercise self-determination, at least in the last 30 years since they became a more democratic society. In a very real, practical sense, they were given self-determination, and perhaps that remains part of the reason behind the American approach to the ambiguity [over Taiwan’s status] .... The American view is that the people of Taiwan should be involved in the ultimate decision about their future.

Wilhelm: There are some scholars who argue that, in fact, Taiwan is a state because of self-determination, and their line of argument is that over the course of the democratization process, the Taiwanese people have participated in the creation of a new state. So it's been self-organized, if you will. What are your thoughts about that?

Dutton: First of all, I agree, Taiwan is a state — or the government on Taiwan represents a state.

Wilhelm: A declaratory state.

Dutton: Yes, a declaratory state. And it continues to exist in sort of rump fashion on the territory that is indisputably Chinese – that is to say, Jinmen and Mazu. It’s a very interesting and complex existence that the government on Taiwan has, because yes, it came out of a history of civil war; it once governed all of China [and] now only governs some small offshore islands that are indisputably China. Plus it governs other territory that is either Chinese territory or Taiwanese territory, one or the other. It's not like anybody else has a claim to the territory.

Wilhelm: This is a really subtle point that you're making, a subtle distinction between the government and its legitimacy and ownership of territory, right? I think what I'm hearing you saying is that perhaps the government of Taiwan has a certain legitimacy through self-determination, but that doesn't mean it owns the land on which it governs.

Dutton: The question is, what is the basis of the legitimacy? I think that's the best way to put it. One is that there is a government on land that is not sovereign to any other state. That's [the island of] Taiwan and the Penghu islands. Governing on that territory as a declarative state is a legitimate separate state. How do you then categorize the authority or the legitimacy that the government in Taipei exercises over Jinmen and Mazu? That thread of legitimacy stems from when the government in Taipei was, in fact, the government of all of China [based] in Nanjing. It still possesses that territory as a residue of its time as the government of all of China. And then of course, similarly, Taiping Island in the South China Sea is something that the Republic of China has possessed.

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Audience question: Why wasn’t the Republic of China or the People’s Republic of China a party to the San Francisco peace treaty? Was it intentional that the peace treaties with Japan left out the sovereignty issue?

Dutton: Neither the People's Republic of China, which was two years old at that point, nor the Republic of China was invited to San Francisco because the victorious powers could not agree on which China to invite. So neither was invited. That's why there was a separate treaty, the Treaty of Taipei, between the Japanese and the Republic of China.

It was very intentional to leave the status of the territory as undetermined. … It was in the interest of the United States to have Taiwan remain separate from the mainland.

It was very intentional to leave the status of the territory as undetermined, based on that Truman statement that by 1951, the Republic of China, to whom the United States had agreed to give the territory, was no longer the government de facto of all of China.

Number two, it was in the context of the Cold War. It was in the interest of the United States to have Taiwan remain separate from the mainland because there was a struggle between communism and the West. The close connection between Mao and Stalin in that period was of serious concern to Truman. So, yes, it was very intentional that the United States, and Britain too, ensured that sovereignty was relinquished by Japan but was not reassigned in the treaty.

Audience question: Were Cairo and Potsdam legal documents that had legal force? Did Truman change the outcome of international law with his change in policy [about returning Taiwan to China after the war]?

Dutton: It is a fair argument to say that the agreement of Cairo, the agreement of Potsdam, and the signature of Japan at the surrender agreement that resulted in an acceptance of the terms of Potsdam should be considered a treaty in its sum total. As I have read the law and the analysis about the law, that is not the best analysis as to whether that amounted to a treaty, but it certainly is a reasonable argument. It's one that the PRC makes, that there was a treaty transfer based on the sum total of the agreements.

Audience question: What are the implications of your argument for the status of the Taiwan Strait?

I am of the view that the claims of the People's Republic of China about the Taiwan Strait ... comply with international law. There are many other people who don't agree with that, but I think that the People's Republic of China claims that there are baselines, there's a territorial sea, and there's an exclusive economic zone in the middle of the strait – they don't say it's not an international strait. When they object to the passage of warships through it, I think what they're really objecting to is the political signaling about warships passing through the strait that's intended to interfere with what, in Beijing's point of view, is a domestic matter.

Audience question: When the Japanese relinquished their sovereignty over Taiwan with the signing of the peace treaty, doesn't it make sense that it would go back to China since it had been taken from China?

This is the retrocession argument. China makes the same argument. ... That's not what international law actually says. International law says it's got to be explicit in a treaty because of the preference in international law for sovereignty and certainty about sovereignty.

Audience question: I guess I don't understand what you mean by a declarative state. What some people might understand… is a state that has declared its independence, as, say, Kosovo has. You can correct me but I don't think Taiwan has done that.

Dutton: I'm not sure you're puzzled. I think you might disagree. And that's okay. There are political entities that meet the four-part test of declarative sovereignty, but are not well recognized by the rest of the international community, and therefore not able to take full part in international society. There's been a rich discussion for a couple hundreds of years about polities that are not fully recognized, but that do have protections of international law as some sort of second-level sovereign. ... Actually, Taiwan does consider itself an independent state as the Republic of China.

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Peter Dutton is a senior research scholar in law and senior fellow at the Paul Tsai China Center at Yale Law School, and a non-resident affiliated scholar of the U.S.-Asia Law Institute.

Suggested citation:

Peter Dutton, “What Does International Law Say About Taiwan?” USALI Talking Points, June 16, 2025, https://usali.org/publications/talking-points-what-does-international-law-say-about-taiwan.

The views expressed are those of the speaker, and do not represent those of USALI or NYU.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.