Asia-Pacific, Power & Security A Legal Perspective on the Future Cross-Strait Relations in William Lai’s Taiwan

The People’s Republic of China (PRC) does not hide its ambition to reunite with Taiwan. In his 2024 New Year’s Day speech, President Xi Jinping emphasized that “China will surely be reunified, and all Chinese on both sides of the Taiwan Strait should be bound by a common sense of purpose and share in the glory of the rejuvenation of the Chinese nation.” Peaceful reunification is always on the agenda, but China will also consider the use of force as a possible option. The warning was directed at “outside forces and the few separatists seeking ‘Taiwan independence’ and their separatist activities.” On the other side of the Taiwan Strait, President-elect Lai Ching-te had previously called himself a “pragmatic worker for Taiwan independence.” Lai’s plan for his presidency was to keep the cross-strait status quo, which apparently went against the reunification aspiration of China. The specter of China’s use of force against Taiwan hangs over the island again.  

From the perspective of international law, there are two questions that need to be answered: (1) whether the reunification between two sides of the Taiwan Strait is an internal affair of China, and (2) whether the use of force against Taiwan by China is legal. I argue that under the light of international law, the answers for these questions are negative and will conclude with certain observations and suggestions for other countries in case there is an unlawful use of force carried out by China against Taiwan.

The Legal Status of Taiwan 

Whether Taiwan is a country and its legal status are longstanding questions in international law and relations. Most answers treat Taiwan as a static concept. This paper takes a different view and argues that the legal status of Taiwan is a revolutionary one. In fact, it changes—and has changed—over time.  

In 1683, Taiwan was placed under the control of the Chinese Empire. Then, in 1895, the island was ceded to the Japanese Empire under the Treaty of Shimonoseki. During the time Taiwan was considered as part of Japan, there were two political entities in China fighting with each other to gain the control of the whole country. The Kuomintang (KMT) lost the Chinese Civil War to the Chinese Communist Party, which then established the People’s Republic of China (PRC), and retreated to Taiwan island in 1949. The complexity concerning the legal status of Taiwan began.

After losing World War II, Japan had to renounce all rights, titles, and claims over Taiwan. The arrangement was found in the Cairo Declaration in 1943 and the Potsdam Proclamation in 1945. However, the legal status of an occupied territory could not be settled until the conclusion of a peace treaty. The 1951 treaty between Japan and the Allies (China was absent from the process) did not specify under which government or which country Taiwan was returned to. At the moment, the Republic of China (ROC) under the KMT effectively controlled the island and was recognized as the sole government of the whole China despite having lost the civil war.  

Since the founding of the United Nations (UN) in 1945 until 1971, the ROC represented China at the UN. More importantly from 1951 to 1971, at the UN General Assembly the ROC and the PRC had competing sovereignty claims over the whole territory of China, including mainland China, Taiwan, and other offshore territories. In 1971, United Nations (UN) General Assembly Resolution 2578 (XXVI) replaced the ROC on the Security Council with the PRC, ending the ROC’s presence at the UN. Nonetheless, the resolution could not deny the fact that the ROC still existed and effectively governed Taiwan.  

For 20 years—from 1971 to 1991—the ROC tried to convince the world of its legitimacy as the government of China but failed. In 1991, the ROC gave up its sovereignty claim over the whole of China. It opened the period of time when the Taiwanese identity started to be realized and developed by the government and the people of Taiwan. Since then, not only has Taiwan considered the relationship between itself and mainland China as a “cross-strait” relation between two governments with equal rights (rather than an internal affairs between the central government and local one), but it also added significant changes in its Constitution. In the 2005 Additional Articles to the Constitution, Taiwan is referred as “the free area of the Republic of China” with defined territory; furthermore, the people of Taiwan are distinguished from the Chinese people from the mainland China, whose relationships are specified by law.  

The idea of a “Taiwanese entity” existing in tandem with China also manifests in several statements of political figures in Taiwan.  For example, while President Xi Jinping characterized the people from two sides of the strait as “all Chinese” of the “Chinese nation,” President Tsai Ing-wen of Taiwan underlined that “Taiwan” is not “China” by regarding the relations with China as foreign affairs like those with the United States, South Korea, Canada, or other countries in the world. What is more, the newly-elected president of Taiwan, Lai Ching-te, once remarked that “Taiwan is already a sovereign, independent country called the Republic of China” and that “the Republic of China and the People’s Republic of China are not subordinate to one another.” 

From the brief history above, there are several points which should not be overlooked. First, Taiwan has never been ruled by the PRC. Second, Taiwan has never formally declared independence. One legal approach to the status of Taiwan in international law is that a claim of statehood must be established for an entity to be regarded as a State; therefore, the absence of such explicit declaration refrained Taiwan from being recognized as an independent country. Nonetheless, it cannot be denied that an entity without statehood status can possess certain rights recognized by international law, such as the right of self-determination. Third, the legal status of Taiwan has evolved. It has changed from “a part of the Chinese Empire,” to a part of China under the control of the ROC who competed with the PRC as the sole government of the whole China, to a special entity democratically governed by the ROC with separate Taiwanese identity from “the Chinese” (see this chart). Therefore, it is insensible to commit to the idea that the reunification of the two Taiwan Strait sides is the “internal affair” of China.

The Use of Force by China Against Taiwan  

The intention of China’s use of force to reunite with Taiwan can be found not only in political statements of its leaders, but also in Chinese domestic legal system. Article 8 of the 2005 China’s Anti-Secession Law states: “In the event that the ‘Taiwan independence’ secessionist forces should act under any name or by any means to cause the fact of Taiwan's secession from China, or that major incidents entailing Taiwan's secession from China should occur, or that possibilities for a peaceful reunification should be completely exhausted, the state shall employ non-peaceful means and other necessary measures to protect China's sovereignty and territorial integrity.” In practice, China has frequently showed off its force around the island. Yet, China has not attacked Taiwan. From a legal perspective, there may be two reasons for such inaction.  

Firstly, international law restricts the use of force by China against Taiwan. Under Resolution 2578, the PRC is a member State of the UN; therefore, it is bound by the UN Charter. Article 2(4) prohibits UN Member States from threatening of using force or actually using force in the manner inconsistent with the Purposes of the UN Charter. According to article 1 of the Charter, among others, maintaining international peace and security is the raison d’etre of the UN. When article 1 is read together with the Preamble of the Charter, it is arguable that “peace” in this case is not just the absence of war, but also includes “the diminution of issues likely to cause war. Likewise, “security” in this case extends from “security between nation States” to “security of the people” (or in other words, human security). Therefore, it will be a flagrant violation of the UN Charter, which is binding on China, if it carries out an armed attack to Taiwan. First, an attack to Taiwan may increase tension between the two nuclear-powers: China and the United States (US), which concomitantly threatens international peace and security. Under Section 2 and 3 of the Taiwan Relations Act, the US is obliged to provides arms necessary for Taiwan to maintain its self-defence capability against any forms of coercion, including the resort of force. In fact, after the 2024 Taiwan election, the US sent its warship transiting through Taiwan Strait, an action commended by China as “provocative.” Second, a war against Taiwan may destroy the economy of the island and cause humanitarian crisis to 23,5 million Taiwanese people.  

Secondly, the law of China itself creates conditions for the use of force against Taiwan. Those conditions are (1) the exhaustion of peaceful reunification, and (2) an attempt of secession from China, including a major incident causing Taiwan’s secession.  As mentioned, Taiwan has never officially declared independence. President-elect Lai expressed the intention to keep peace in Taiwan Strait and did not rule out the possibility of conducting dialogue between the two sides of the Strait. Therefore, it is difficult to argue for the establishment of the two conditions in China’s 2005 Anti-secession law to justify the use of force against Taiwan.  

The lack of legitimacy based on both international and domestic law and the risk of reputation cost are high in this situation. Hence, it is unwise for China to carry out an armed attack to Taiwan. This can also explain why China has been increasingly employed the gray-zone operations tactics in Taiwan Strait, but it is beyond the scope of this paper to discuss such issue.  

Conclusion 

Although Taiwan is not an entity possessing full statehood status, it exists in the international legal system with certain rights, including the right of self-determination. The reunification of the two sides of the Taiwan Strait, therefore, is not an internal affair of one party to the issue. As long as Taiwan is able to keep the status quo in the relationship with its counterpart across the strait, it is difficult for China to find compelling justification in international law as well as in its domestic legal system for its unilateral use of force to impose control over Taiwan.  

The international community, nonetheless, has to prepare itself in the case of an invasion happening in Taiwan Strait. Adeptly employing legal tools can be seen as both sensible and impartial in this highly political sensitive situation. The recent cases between Ukraine and Russia as well as between South Africa and Israel concerning the Israeli war against Hamas in the Gaza are two primary examples of it. Therefore, in the event where China carries out a military offensive to bring Taiwan under its control, UN Member States, via the General Assembly, could bring the case before the International Court of Justice. To be more specific, the Assembly could ask for advisory opinion of the Court about the right of self-determination of the people in Taiwan and the responsibilities of the UN and its member States if the right is forcefully denied. The opinion of the Court will offer legitimacy for countries to gather support for Taiwan without drawing to a political maelstrom of the war.