Why Taiwan Has No International Legal Recourse Over Beijing’s M-503 Bullying

Why Taiwan Has No International Legal Recourse Over Beijing’s M-503 Bullying

Why Taiwan Has No International Legal Recourse Over Beijing’s M-503 Bullying

Julian Ku is the Maurice A. Deane Distinguished Professor of Constitutional Law at Hofstra University School of Law. He is a co-founder of Opinio Juris, the leading blog on international law.

Beijing’s unilateral declaration at the outset of 2018 that it would allow new usage of commercial air route above the Taiwan Strait understandably caused new cross-Strait tensions. Yet, despite some opinions to the contrary, Beijing’s actions do not violate international law and the M-503 south-north flight route kerfuffle highlights just one more example of the many ways in which Beijing can act—consistently with international law—to bully, isolate, and damage Taiwan’s interests. For this reason, the M-503 episode should remind Taiwan’s leaders that, as long as it continues to exist as an entity unrecognized by most countries and not as a sovereign state, Beijing can use international law to isolate and undermine Taiwan’s interests.


M-503 is an international designation for a flight route between eastern China and southern China that lies just 7.4 kilometers (4.5 miles) away from the de facto border separating the People’s Republic of China (PRC) and Taiwan over the Taiwan Strait. The flight route, which is used by commercial airlines traversing between destinations such as Shanghai and Hong Kong, did not begin to be used until 2015. At that time, Beijing and Taipei agreed to use the route for north-south flights only. Beijing had sought to open up the route for flights in both directions, but had reportedly agreed to limit usage out of deference to objections raised by then-Taiwan President Ma Ying-jeou.

On January 4, 2018, Beijing announced it would allow commercial flights in both directions on M-503, as well as extend existing flight routes closer to Taiwan’s Air Defense Identification Zone (ADIZ). This drew objections from Taipei because Beijing did not consult with Taiwan before making the announcement. Such consultations, Taipei has asserted, have been the usual agreed practice between the two sides on questions of commercial flight routes in and around Taiwan. Beijing replied that it did not need any authorization from Taiwan to act on the flight routes. This led to Taipei cancelling certain flights between Taiwan and China during the Lunar New Year Holiday.

Taipei’s objections to M-503 arise from the fact that commercial airlines flying along that air route complicate Taipei’s maintenance of an ADIZ to monitor possible military threats to its airspace. Along with other routes recently extended by Beijing near the Chinese cities of Xiamen, Fuzhou, and Dongshan, full Chinese usage of the M-503 route makes it more difficult for Taiwan to control its airspace by authorizing commercial air traffic near or even within Taiwan’s ADIZ.

Legal Framework

As a matter of international law, the designation of flight routes is coordinated through the International Civil Aviation Organization (ICAO), an agency of the United Nations. The ICAO is an international organization authorized by its member-states to administer and manage the Chicago Convention on Civil Aviation. The Chicago Convention serves the legal foundation for international cooperation in the management of international civil aviation. The ICAO creates regulations and standards related to civil aviation and facilitates agreements between countries on international flight routes that affect national airspace.

It is important to note that countries have not delegated to the ICAO any specific authority to designate flight routes over international airspace. But the ICAO is the key institution where technical experts work together to develop flight routes that are eventually implemented by national authorities. Taiwan, as the Republic of China, has been excluded from the ICAO since 1971, when it lost its seat at the United Nations Security Council to the PRC. Taiwan’s representatives have sometimes participated in ICAO meetings as a “guest” of the ICAO president, but Taiwan does not otherwise have any formal role in the ICAO, even though its civil aviation agency follows ICAO rules and standards as closely as possible.

In this legal sense, China’s decision to open the M-503 flight route to south-north traffic did not require the ICAO’s approval. However, that route had been developed in consultation with an ICAO Working Group since ICAO’s support for the flight route gives China international legitimacy for its decision on M-503, even if Beijing is not strictly required by the Chicago Convention or international law to seek ICAO approval.


Because Taiwan is not a member-state of the United Nations, it also cannot be a member-state in the ICAO, which is a specialized UN agency. Taiwan’s exclusion from the ICAO, a technical agency tasked with practical rather than political issues, seems unfair and unwise. Indeed, Taiwan’s diplomats have noted that Taiwan is a significant air traffic hub and that it has technological expertise it can share with other countries through the ICAO.

Taiwan has also used this type of pragmatic argument to lobby for inclusion in activities of the World Health Assembly. Indeed, there are many parallels between Taiwan’s exclusion from the ICAO and its exclusion from the WHO. Both organizations are specialized UN agencies focused on fostering international cooperation on non-political technical issues, like air safety and health. In the past, Taiwan has been able to participate as a non-member in both organizations with the support of its allies and, most crucially, with the acquiescence of China. While China does not have a formal veto power in either organization, the consensual nature of those international agencies makes it difficult for them to defy the opposition of one of its members over the admission of an observer or “visiting” participant like Taiwan.

This episode is a good example of why international law almost always works in favor of Beijing, and against Taiwan. Nothing that China has done in blocking Taiwan from participating in the ICAO or in rejecting Taiwan’s opposition to its new flight routes is a violation of international law, or ICAO regulations. As a legal matter, China is perfectly within its rights to exercise its power to authorize flights over the routes it has developed in coordination with the ICAO. Taiwan is not formally a member of the ICAO and does not have any legal rights to object to the flight routes or Beijing’s use of it. As a state not recognized by most countries in the world and not being a member of the United Nations, Taiwan has almost no rights under international law, despite the compelling moral and pragmatic arguments it has advanced for its people.

Risks for Beijing

It is not surprising, therefore, that Beijing has used its legal advantage by excluding Taiwan from the WHA and the ICAO. To do otherwise undermines Beijing’s strict definition of its “One-China” principle and is a useful way to pressure the Taipei government. By denying Taiwan the practical benefits of participation in international organizations, Beijing reminds Taipei of the disadvantages of Taiwan’s refusal to endorse Beijing’s “One-China” principle.

Yet, there are risks for Beijing in pressing its advantage too far. By closing off every avenue for allowing Taiwan’s participation in international organizations like the ICAO, Beijing risks empowering forces in Taiwan supporting formal independence. Such advocates might argue that because Taiwan cannot, as the ROC, gain recognition in such organizations, it might as well try its luck as an independent Republic of Taiwan. While China would resist any efforts by an independent Taiwan to enter international organizations, independence advocates could point out that China is already blocking such efforts anyways. A formal declaration might, in this view, garner a fresh round of international support and would likely have a stronger claim to recognition under international law. With respect to international law, Beijing holds all the cards. But that doesn’t mean it should play all of them.  

The main point: China’s unilateral modification to sensitive flight routes over the Taiwan Straits is a departure from past practice and a blatant attempt to pressure the Taipei government. Nonetheless, China’s action does not in any way violate international law. What this episode illustrates is how China can use its status as a recognized state to injure and bully Taiwan on the international stage, and, under international law, there is not much Taiwan can do about it.

[1]  I am not advocating such a declaration, but that just pointing out that this danger is something Beijing should consider.