Following Chiang Kai-shek’s (蔣介石) withdrawal from the United Nations (UN) in 1971 as a result of UN Resolution 2758, international recognition of Republic of China (Taiwan) statehood has declined significantly. The contested status of Taiwanese statehood has further complicated efforts to defend the island under international law. As a nation without formal membership in the United Nations and few official diplomatic allies, Taiwan exists in a gray zone where the laws governing interstate relations become difficult to apply. However, following Russia’s invasion of Ukraine and the significant ramping up of the People’s Liberation Army’s (PLA) military incursions in the Taiwan Strait, it has become critical to assess the legality of defending Taiwan in the event of a Chinese invasion. Currently, the most widely accepted interpretation of statehood—outlined in the 1933 Montevideo Convention—is rather narrow, and is invoked by the People’s Republic of China (PRC) to keep Taiwan isolated from international military aid. (See further discussion below.) However, despite the PRC’s attempts to dictate the legal status of Taiwan, Taipei and its supporters could put forward alternative interpretations of statehood that could elevate Taiwan’s international status and legitimize the island’s defense.
The Shortcomings of Current International Law
Historically, the United Nations Charter has served as an instrument of international law that member states are required to uphold. Since international law largely depends on an agreement between parties, institutions like the UN lack a competent means of law enforcement. Therefore, it is critical to recognize international law as a primarily theoretical framework under which states operate.
When it comes to displays of force and matters of defense, however, the UN Charter fails to provide adequate parameters, particularly in the context of contested states. There are two articles that have defined the debate surrounding rights to defense: Article 2(4) and Article 51. Article 2(4) of the UN Charter prohibits “the threat or use of force against the territorial integrity or political independence of any state.” Meanwhile, Article 51 guarantees the “inherent right of individual or collective self-[defense] if an armed attack occurs against a Member of the United Nations.” In the case of Taiwan, both articles rely on the question of whether Taiwan possesses the characteristics of a “state” as such.
In addition to the uncertainty surrounding Taiwanese statehood, there are also a variety of avenues through which the PRC legalizes and justifies the use of force. The PRC has long advocated for an “all-or-nothing” interpretation of international law, relying mainly on a Westphalian understanding of international relations—which maintains that states have absolute power over happenings within their borders, and that international law can only be applied to relations between states. Since the PRC regards Taiwan as an integral part of its territory, Beijing would almost certainly frame any potential military clash as either an internal insurrection or a civil war. Thus, the PRC would portray any international intervention as a violation of its territorial integrity. Under a literal reading of the articles in question, use of force against Taiwan would not be prohibited, as the island lacks official standing as a sovereign state. Specifically, “since Taiwan is not unquestionably a state, international law on the use of force does not apply.”
How the PRC Manipulates the Current Definition of Statehood
The most widely accepted definition of statehood was provided by the 1933 Montevideo Convention on the Rights and Duties of States, which the United States ratified in 1934. According to the convention, a state must fulfill the following four criteria to qualify for statehood: a permanent population, a defined territory, a government, and the capacity to enter into international relations. With a population of around 23.1 million, clear and stable boundaries, a government under the constitutional framework of the Republic of China (ROC), and 14 official diplomatic allies, Taiwan seemingly meets all four criteria. However, Taiwan’s contested status reveals the constraints and shortcomings of such international legal frameworks. Therefore, it is critical to recognize that while these four factors lay out a broad framework for defining statehood, they are merely “necessary and not sufficient on their own for statehood.”
This situation has influenced extensive scholarly discussions, through which two competing theories of statehood emerged: constitutive and declaratory theory. According to a definition provided by the Tsinghua China Law Review, “constitutive theory holds that an entity has to be ‘legitimized’ as such by other states in order to be a state, while declaratory theory considers the existence of a state as a question of fact and not of law.”  However, the constitutive definition of statehood lends itself to easy manipulation by the PRC. Considering Taiwan’s lack of international recognition, the PRC can advocate for interpretations of statehood that further marginalize Taiwan in the international community.
In addition to the PRC’s support of constitutive theory, Liu Yulin of the Tsinghua China Law Review contends that “the practice of admission to the UN virtually discards the declaratory theory of statehood.” Article 4 of the UN Charter requires that “the admission of any such state to membership in the UN will be effected by a decision of the General Assembly upon the recommendation of the Security Council.” As a result, the PRC’s seat on the UN Security Council has created yet another legal barrier to the defense of Taiwan. As a member of the Security Council, the PRC has the ability to veto any motion calling for Taiwan’s admission into the UN. This further precludes Taiwan from enjoying the benefits and protections that would accompany UN membership.
Image: George H.W. Bush (center-right, facing away), then the US Ambassador to the United Nations, confers with ROC Foreign Minister Chow Shu-kai (center) and ROC Ambassador to the United Nations Liu Chieh (left) on October 18, 1971, at the outset of the proceedings that ultimately transferred the “China” UN seat from the ROC to the PRC. Taiwan has had no UN representation since that time, which the PRC has leveraged to deny Taiwan’s legitimacy as a state. (Image source: United Nations)
Legal Ambiguities in US Policy on Taiwan’s Defense
Currently, the defining US policies supporting the defense of Taiwan are outlined in the Taiwan Relations Act and President Ronald Reagan’s “Six Assurances.” The Taiwan Relations Act, which serves as the cornerstone of US policy towards Taiwan, stipulates that the “United States shall provide Taiwan with arms of a defensive character and shall maintain the capacity of the United States to resist any resort to force or other forms of coercion that would jeopardize the security, or social or economic system, of the people of Taiwan.” However, the ambiguous wording surrounding the “capacity of the United States to resist any resort to force” makes it an insufficient legal commitment to Taiwan’s defense. Consistent with the Taiwan Relations Act, the “Six Assurances” serve as another premise for coming to Taiwan’s defense. However, they also include a statement that the US has “not agreed to take any position regarding sovereignty over Taiwan.” Therefore, while there are existing legal agreements that touch on the defense of Taiwan, they do not constitute an explicit guarantee. To avoid violating existing international legal frameworks, the US has maintained a relatively noncommittal stance on Taiwan’s defense. However, so long as the US relies on such ambiguous statements and precedents, the PRC will continue to be able to manipulate discussions of Taiwan’s legal status on the international stage.
Adopting a New Definition of Statehood
While altering the text of the UN Charter to be more inclusive is highly unlikely, the issue of defending Taiwan remains salient. Therefore, it is up to international actors such as the United States to formulate a coherent response. This would not necessarily involve the establishment of official diplomatic ties, but could instead focus on framing a new and broader definition of what constitutes statehood.
While Taiwan lacks official international recognition in the form of diplomatic relations, it possesses other major attributes of statehood: a territory, a robust civil society, a vibrant democracy, a military, and diplomatic relationships (whether formal or otherwise) with other states. Additionally, although the United States does not formally recognize Taiwan, its “cultural, economic, and military ties to Taiwan show that the [US] effectively treats Taiwan like an independent state.”
Thus, the United States and like-minded countries should reject the constitutive argument and advocate for a declarative approach to statehood. This show of support would send a clear message to the PRC that its continued efforts to redefine statehood under narrow terms will not be tolerated. If states can develop a coordinated approach by supporting the declarative theory of statehood, they can apply gradual pressure and potentially loosen the rigid restrictions that have been placed around Taiwan. The declarative approach would enable individual international actors to determine Taiwanese statehood on a case-by-case basis. In turn, this could legitimize international involvement in the event of an armed conflict.
While the current definition of statehood has raised legal questions about whether coming to the defense of Taiwan would be permitted under international legal frameworks such as the UN Charter, these limitations could be remediated. The PRC aggressively presses legal arguments that enforce a narrow interpretation of constitutive statehood. The US and like-minded countries should push back against this and advocate for a newer, more inclusive, declarative definition of statehood. In doing so, they could potentially provide a legal basis for stronger and clearer international commitments to Taiwan’s defense. The US Department of State has already recognized Taiwan as an important partner in “trade and investment, health, semiconductor and other critical supply chains, investment screening, science and technology, education, and advancing democratic values.” Given this strong partnership with Taiwan, ensuring that proper avenues exist for its defense will be critical to preserving and safeguarding the island’s democracy.
The main point: As tensions rise in the Taiwan Strait and the PRC increases its coercive aggression, the defense of Taiwan is becoming an increasingly salient issue that requires international action. Therefore, developing a new definition of statehood, one that would further legitimize and bolster international commitments to Taiwan’s defense, is critical.
 Constitutive theory posits that recognition from other states is required for statehood, while declaratory theory merely considers international recognition as support of the fact that the sovereign state already exists.