PRC Uses Legal Warfare to Support Maritime Blockade Against Taiwan

Executive Summary:

• Creative legal strategies have been deployed in recent years to support a justification for a blockade around Taiwan.
• International law contains the concept of a “long-distance blockade” and the “continuous voyage doctrine” that could both be invoked to restrict access to Taiwan by the international community in the event of a blockade.
• Domestic laws such as the China Coast Guard Law and the Maritime Traffic Safety Law reinforce the foundation for a blockade by empowering the China Coast Guard and People’s Liberation Army Navy to intercept, detain, and regulate foreign vessels in contested waters.

On February 26, Taiwan’s Ministry of Defense reported that People’s Liberation Army (PLA) fighters and warships had set up a zone 40 miles from the island’s southwestern coast to conduct “live-fire drills” (射击训练) without providing customary notification (Military News Agency, February 26). The following day, a spokesperson for the People’s Republic of China’s (PRC) Ministry of National Defense rebuffed this as “pure hype” (纯属炒作) but did not comment on the substance of Taiwan’s reports (MND, February 27). Part of the reason for the alarm was that it followed on the heels of a live-fire drill conducted by a PLA Navy task force in the Tasman Sea, for which the PLA also did not provide appropriate warning (China Brief, March 11). Both instances were legal under international law but constituted unusual and aggressive actions by the PRC. Military pressure on Taiwan has been acute in recent years. In the last twelve months, the PLA conducted “Joint Sword” exercises in May and October and an unprecedented large-scale winter naval training in December (China Brief, July 26, 2024, November 1, 2024, December 20, 2024). These simulated aspects of a blockade suggest that this could be Beijing’s preferred course of action in an operation against Taiwan.

The legal implications of a “Taiwan blockade” are currently under-defined. One text that sheds light on potential legal justifications for a blockade is a chapter in the 2020 publication Research on Key Operational Models in the Law of Maritime Military Actions (海上军事行动法部分重要行动样式研究), co-authored by Han Xiaofeng (韩晓峰) and Shao Jingjing (邵晶晶), researchers at the PLA’s National Defense University. [1] The chapter focuses on a “sea blockade operation” (海上封锁行动), detailing several ways in which the PRC might attempt to deploy and justify a blockade while mitigating international responses. Since the book was published, the PRC has enacted several domestic laws and regulations that lay the groundwork to permit such a course of action.

International Law With Chinese Characteristics

Two approaches to maritime blockades form the legal and operational foundation of the PRC’s evolving approach to maritime control around Taiwan, according to Han and Shao. These are the “long-distance blockade” (远程封锁) and the “continuous voyage doctrine” (连续航程理论). The first, also known as a “distant blockade,” involves intercepting enemy maritime trade at extended ranges, often beyond the vicinity of the adversary’s coastline. Britain imposed long-distance blockades against Germany in both world wars. [2] There is no clear international legal standard defining the operational range of a blockade. Instead, effectiveness is judged by the capacity to deny access to enemy ports. For instance, a blockade reaching 1,000 nautical miles—approximately the distance from Taipei to Beijing—could still be permissible under one interpretation of international law, provided the PRC could effectively enforce it. Beijing thus could escalate blockade measures and extend their scope as it sees fit. By gradually tightening blockade measures, Beijing could restrict Taiwan’s trade flows as a form of economic coercion without immediately triggering an armed response. In this way, the legal ambiguity provides space for the PRC to push the bounds of the law, for instance to justify deploying PLA Navy and China Coast Guard vessels to disrupt Taiwan-bound shipping.

The continuous voyage doctrine is a principle of international law that allows the seizure of goods, including contraband (i.e. military goods), if there is a clear intent to transport them to an enemy state. Initially rejected by many states, the doctrine gained acceptance after World War II as countries refrained from challenging its application in international customary law. It was applied during the two world wars and the blockade of the Gaza Strip, setting a precedent for broad enforcement. [3] If the PRC were to invoke it against Taiwan, neutral vessels transporting goods to Taipei or Taiwan-controlled islands could be intercepted and searched, including in international waters. Unlike a traditional blockade, which is geographically constrained, enforcement of the doctrine would allow the PRC to interdict shipments globally.

Restrictions Short of a Blockade

Under the law of war, the legality of a maritime blockade is contingent on the existence of an international armed conflict. The United Nations Convention on the Law of the Sea designates the Taiwan Strait as international waters. Under this designation, a blockade of Taiwan could be legitimate in the event of an armed conflict. However, Beijing’s long-standing political position is that all Taiwan-related matters are the PRC’s internal affairs. Under this view—which runs counter to international law—a military operation over Taiwan would be classed as a non-international armed conflict. As such, a blockade beyond the PRC’s territorial waters lacks a clear basis in international law. Some scholars argue that principles governing blockades can be extended to non-international conflicts if they align with international humanitarian law (IHL). However, this remains a legally contentious position and it is unclear how Beijing might seek to make such a justification. [4] Given these constraints, the PRC may pursue one of two alternative strategies to restrict Taiwan’s maritime access without formally declaring a blockade.

One approach would be to designate zones under security-related pretexts without explicitly instigating a blockade. This has a precedent in the Guanbi (关闭; closed port) Policy employed by the Republic of China in 1949 during the civil war, which involved laying mines and restricting shipping routes along China’s coastline to disrupt Communist-controlled ports. Beijing could employ similar methods against Taiwan to achieve a comparable effect without formally declaring a blockade. Another tactic could be designing maritime danger zones, citing safety concerns related to military exercises. Although these zones may not carry the same legal weight as a declared blockade, the PRC could still use them to pressure foreign commercial and military vessels to avoid certain shipping routes. This tactic has been used previously, including during the 1995–96 Taiwan Strait Crisis and the 2022 live-fire exercises following then-Speaker Nancy Pelosi’s visit to Taiwan. The two instances in the Tasman Sea and southwest of Taiwan in late February this year could signal that Beijing favors this tactic.

A second approach could be pursued if the United States or other actors intervene militarily in a Taiwan conflict. In this scenario, the PRC could invoke individual or collective self-defense under Article 51 of the UN Charter to justify a more forceful maritime interdiction strategy. The PRC might then establish a maritime exclusion zone or total exclusion zone around Taiwan, restricting access to certain areas under the guise of preventing foreign interference. [5] Within such a zone, PLA or China Coast Guard ships could interfere with other ships’ communications and capture or even attack vessels that failed to comply with instructions. [6] This approach aligns with the PRC’s broader legal position of interpreting international law in ways that advance its objectives while maintaining plausible deniability against accusations that it is instigating a conflict (Japan-Taiwan Exchange Foundation, May 2023).

New Laws Legitimize Blockade Operations

Since the publication of Han and Shao’s book, the PRC has passed laws and created regulations to create a legal basis for imposing maritime control around Taiwan.

The China Coast Guard Law (海警法), which came into effect on February 1, 2021, formalizes the duties and powers of the coast guard, granting it robust enforcement authority in “maritime areas under PRC jurisdiction” (中华人民共和国管辖海域) without defining the extent of those areas (MFA, January 22, 2021). [7] The law also authorizes the China Coast Guard to “take all necessary measures, including the use of weapons” (采取包括使用武器) against perceived infringements of PRC sovereignty or jurisdiction and to expel foreign vessels from waters the PRC claims. If a foreign military or government ship enters waters the PRC considers its own and refuses to comply with PRC demands, the law permits measures up to the removal of that ship by force. Additionally, the coast guard may establish “temporary maritime security zones” (海上临时警戒区) in which ships and personnel can be restricted or prohibited from entering and requisitioning civilian assets in emergencies. These zones can be established outside of wartime and under broad pretexts. Xinhua, the PRC’s state news service, describes the law as a “powerful legal guarantee” (有力法律保障) for the coast guard “to safeguard national sovereignty, security, and maritime rights and interests” (维护国家主权、安全和海洋权益). In PRC discourse, the law is framed as closing gaps in maritime “rights protection” (维权) enforcement, effectively weaponizing law enforcement to serve national security goals (Xinhua, January 23, 2021)

The Regulations on Administrative Law Enforcement Procedures for Coast Guard Agencies (海警机构行政执法程序规定), which came into effect on June 2024, supplements the Coast Guard Law (CCG, June 15, 2024). It empowers the coast guard to detain foreign vessels and persons for up to 60 days and to implement temporary maritime “warning zones” (警戒区) for military purposes. This further expands the coast guard’s ability to prevent violations of the PRC’s sovereignty and jurisdiction and to enhance its law enforcement capabilities (China Brief, June 21).

In September 2021, the PRC’s legislature adopted a sweeping revision of the 1983 Maritime Traffic Safety Law (海上交通安全法) (Xinhua, April 30, 2021). The amended law greatly expands the PRC’s authority over foreign vessels in and near its waters. It applies to “sea areas under the jurisdiction of the PRC” (中华人民共和国管辖海域) without clearly defining them. Article 54 compels certain foreign ships to notify PRC maritime authorities upon entering its territorial waters. The revised law also affirms the PRC’s authority to alter or suspend maritime traffic in areas it designates for security or military purposes. The PRC can also strictly control activities in these waters by specifying the types of foreign ships that must provide information when navigating and anchoring in “pilotage zones” (引航区)—specific geographical areas where the safe and efficient navigation of vessels requires the assistance of a qualified pilot. (Indo-Pacific Defense Forum, March 21, 2022). Although authorities generally establish pilotage zones in ports, bays, and inland seas that receive a high volume of foreign maritime traffic, the PRC can, under this law, define a pilotage zone as a disputed area, even if it is within another country’s exclusive economic zone. The law raises penalties for violations, including fines and detentions of vessels. While it is unclear that aspects of this law accord with international law, the threat of punishment by the PRC that it entails bolsters the credibility of a potential blockade by warning ship owners and insurers that attempting to breach a PRC-declared blockade could have negative legal consequences.

In addition to the above maritime-focused regulations, the PRC has updated broader defense legislation that also could be used to facilitate a blockade. A revised National Defense Law that took effect in January 2021 grants the Central Military Commission the power to “safeguard … developmental interests” (保卫 … 发展利益) and oppose secession (MND, December 27, 2020; China Brief, February 26, 2021). This enables the military’s top leadership to initiate operations not only for immediate defense but also for protecting national unity and other interests (Indo-Pacific Defense Forum, January 28, 2021). The Outline on Military Operations Other Than War (军队非战争军事行动纲要（试行)), which Xi Jinping signed in 2022, provides guidelines for the PLA to undertake missions that can strengthen the testing of PLA combat capabilities, enhance the PLA’s implementation of gray zone operations, and expand the role of the military’s operation (Xinhua, June 13, 2022; INDSR, June 23, 2022). This has led to speculation that Beijing could frame an action targeting Taiwan as a “special military operation” and deploy domestic law to assert the legitimacy of its actions, just as Russia has done in Ukraine.

Conclusion

Beijing has spent the last several years constructing a domestic legal toolkit that will allow it to claim a blockade against Taiwan as legitimate or reinforce the foundation for a blockade by empowering the China Coast Guard and PLA Navy to intercept, detain, and regulate foreign vessels in contested waters. As PLA-affiliated researchers laid out in 2020, avenues for justifying such actions under international law also have been explored. As a formal blockade would implicitly recognize Taiwan as a belligerent, contradicting the PRC’s “One China Principle” (一个中国原则), Beijing may seek an alternative. These could include establishing exclusion zones or maritime danger zones. In the event of U.S. intervention, Beijing could also invoke self-defense to establish a maritime exclusion zone or a total exclusion zone.

A de facto or de jure blockade of any length would significantly impact Taiwan, which is heavily reliant on imports. Beijing may frame such an act as economic coercion rather than military aggression to avoid backlash and delay an international response. Upholding international law, protecting open shipping lanes for regional states whose goods are shipped through the Taiwan Strait, and preserving peace are in the interests of all nations. However, concerted efforts will be required to push back against the PRC’s increasing legal warfare as it attempts to achieve the “unstoppable historical trend of national unification” (谁也不能阻挡祖国统一的历史大势) (MFA, December 31, 2024).

Notes

[1] Han Xiaofeng 韩晓峰 and Shao Jingjing 邵晶晶. Haishang junshi xingdong fa bufen zhongyao xingdong yangshi yanjiu. 海上军事行动法部分重要行动样式研究 [Research on Key Operational Models in the Law of Maritime Military Actions]. Beijing: Shishi Chubanshe, 2020.

[2] Michael G. Fraunces, “The International Law of Blockade: New Guiding Principles in Contemporary State Practice,” The Yale Law Journal, Vol.101, 1992, p.900–901.

[3] Phillip Drew, The Law of Maritime Blockade: Past, Present, and Future, Oxford University Press, 2017, p.56, 79–80.

[4] Liu Ranran and Fan Chen, “A study on the legal protection of maritime blockade operations in high-end naval warfare” [高端海战中海上封锁作战法律保障问题研究], Defence Industry Conversion in China [中国军转民], 2024(17):3 5-37., and Zhu Lijian, “Haishang fengsuo guojifa zhong de liyi pingheng: Chuantong, dangdai yu tiaozhan” 海上封锁国际法中的利益平衡：传统、当代与挑战 [The balance of interests in international law of maritime blockade: tradition, contemporary issues, and challenges], Journal of Shenzhen University (Humanities & Social Sciences), Vol.38 No.6, November 2021.

[5] A maritime exclusion zone is a designated area at sea established by a belligerent nation during armed conflicts to control or prohibit access to foreign ships and aircraft. Unlike traditional blockades, which involve close deployment near enemy ports to prevent ingress and egress, these zones cover extended areas where offending vessels can be subject to attack rather than confiscation. A total exclusion zone is a more stringent form of exclusion zone wherein any vessel or aircraft, regardless of its national affiliation, entering the designated area may be subject to attack without prior warning. The United Kingdom instituted such a zone during the Falklands War, designating all vessels and aircraft that entered within 200 nautical miles of the Falkland Islands, including those of neutral countries, as targets without warning. See British Year Book of International Law, Vol.53, 1982, 539 and 541–542.

[6] San Remo Manual on International Law Applicable to Armed Conflicts at Sea, International Institute of Humanitarian Law, June 12, 1994. §108.

[7] Although there is no specific definition of the relevant sea areas, according to the PRC’s Supreme People’s Court, “the internal waters, territorial seas, contiguous zones, exclusive economic zones, continental shelves and other sea areas under the jurisdiction of the People’s Republic of China.” The draft of the Coast Guard Law initially had a similar provision that was deleted from the final text (see Japan Ministry of Defense, March 16, 2021; CSIS, June 7, 2023).