Introduction

This article reviews China’s heavy-handed response to an announcement by Japan and the Philippines that they intend to delimit their exclusive economic zone (EEZ) maritime boundary east of Taiwan. It will first briefly discuss the some of the outcomes of the May 2026 Japan-Philippines Summit meeting, where the two nations announced (inter alia) their intention to delimit their maritime boundary. It will then discuss China’s diplomatic response to the proposed delimitation, as well as China’s special maritime law enforcement operation east of Taiwan intended to discourage Japan and the Philippines from negotiating the boundary agreement without China’s participation. The article will then discuss the relevant international law applicable to maritime delimitations and the authorities coastal States enjoy over foreign-flagged vessels in the various maritime zones. The article will next review the legality of China’s unprecedented special maritime law enforcement operation and will conclude with the observation that the operation was inconsistent with international law, as it impeded high seas freedoms of navigation of foreign-flagged vessels and violated the principle of exclusive flag State jurisdiction applicable beyond the territorial sea.

Japan-Philippines Summit Meeting

During a state visit to Japan from May 26-29, 2026, President Romualdez Marcos and Prime Minister Takaichi Sanae held a summit meeting in Tokyo to celebrate the 70th anniversary of the normalization of diplomatic relations between Japan and the Philippines. At that meeting, the two leaders decided to elevate their bilateral relations to a Comprehensive Strategic Partnership. Among other things, both leaders “reaffirmed the need to further promote peace, stability, and mutual trust through maritime cooperation underpinned by respect for international law” and decided to “commence formal negotiations to delimit the maritime boundary of the EEZ and the continental shelf between the two countries” east of Taiwan to enhance legal certainty in the region.[i]

The two leaders also expressed their “serious concern over the situation in the East China Sea and South China Sea,” reaffirming their “strong opposition to any unilateral attempts to change the . . . status quo by force or coercion” and emphasizing the “importance of upholding freedom of navigation and overflight, lawful uses of the sea, unimpeded commerce, and the peaceful resolution of maritime disputes in accordance with international law.” [ii] The two leaders “reiterated their support for the 2016 South China

Sea Arbitration Award,” as well as the “importance of peace and stability across the Taiwan Strait,” encouraging the peaceful resolution of cross-Strait issues through dialogue. [iii]

China’s Diplomatic Response

Beijing immediately condemned the “unauthorized initiation of so-called maritime boundary delimitation negotiations,” stating that the negotiations would seriously infringe on China’s maritime rights and interests and are “completely illegal and invalid.”[iv]

Chinese Foreign Ministry Spokesperson Mao Ning asserted that China possesses an EEZ and continental shelf in the area in question and that the negotiations would not “affect China's claims to rights in the waters east of Taiwan or its exercise of its legitimate rights.”[v] Accordingly, Mao Ning maintained that, consistent with international law, any delimitation concerning waters east of Taiwan would require “China as a party to the talks,” as both sides of the Taiwan Strait belong to China and all Chinese people “have a shared responsibility to uphold national sovereignty and maritime rights and interests.”[vi] She further urged Japan and the Philippines “to immediately cease any actions that infringe upon China's maritime rights and interests, and to take concrete actions to safeguard regional peace and stability.”[vii] Mao Ning also stated that “any negotiations that do not include China would constitute a violation of the United Nations Convention on the Law of the Sea (UNCLOS) and other international laws and basic norms governing international relations.”[viii]

Ocean University of China Law School Professor Yu Minna also emphasized that the ongoing territorial dispute between Japan and China over the Senkaku Islands (Diaoyu Dao) could be affected by the proposed negotiations. Specifically, she reiterated that the delimitation of the East China Sea remained unresolved and that the Senkakus (Diaoyus) were connected to the main island of Taiwan, that the islands were “Chinese territory since ancient times,” and that China’s claimed “continental shelf in the East China Sea extends naturally to the Okinawa Trough.”[ix] Japan’s attempt to legitimize its illegal claims in the East China Sea by negotiating a maritime boundary with the Philippines would “exacerbate regional tensions and elevate the risk of geopolitical conflict.”[x]

Professor Yu Minna further pointed out that China and the Philippines share extensive overlapping EEZ and continental shelf claims in the Bashi Channel, which is located between the island of Taiwan and the Philippine archipelago. By concluding a bilateral delimitation agreement with Japan, Manila would “create a fait accompli” and “open a second battlefield outside the South China Sea to unlawfully encroach upon China’s maritime rights and interests.”[xi]

Finally, Professor Yu Minna argues that the bilateral negotiations would allow Japan to secure de facto recognition of its illegal EEZ and continental shelf claims off Okinotorishima, spanning over 40,000 square kilometers. Such a result would damage the collective interests of the international community. Okinotorishima is purportedly a rock, not an island, and is therefore not entitled to claim an EEZ or continental shelf.

In short, China asserts that the bilateral maritime delimitation negotiation between Japan and the Philippines is a grave violation of international law. First, it severely infringes on China’s lawful maritime rights as a coastal State. Second, it violates the obligations regarding maritime delimitation under articles 74 and 83 of UNCLOS. Third, it openly flouts the fundamental principle of third-party consent in international law. Finally, the bilateral negotiations and any subsequent arrangements cannot affect or diminish China's sovereignty and lawful claims—that is, a treaty does not create either obligations or rights for a third state without its consent.[xii]

China’s Special Maritime Law Enforcement Operation

In addition to its diplomatic response, China also engaged in heavy-handed maritime law enforcement operations to intimidate Japan and the Philippines, as well as interfere with the navigational rights and freedoms of the international community. Beginning on June 1, 2026, two China Coast Guard (CCG) vessels (Daishan (CCG-2502) and Bai Ta (CCG-2304)) conducted law enforcement patrols east of Taiwan, purportedly to directly target “the illegal collusion between Japan and the Philippines.”[xiii] CCG patrols in these waters are intended to defend China’s territorial sovereignty and are justified as a “forceful response to unlawful maritime encroachment.”[xiv] Chinese officials warned that, if the bilateral discussions continue, they “will be met with a corresponding increase in China’s countermeasures.”[xv]

Several days later, on June 6, 2026, China’s Ministry of Transportation, in coordination with the Fujian and Guangdong maritime safety administrations, the East China Sea Navigation Support Center, and the East China Sea Rescue Bureau, launched a five-day special maritime law enforcement operation in waters east of Taiwan. The purpose of the operation is to “fully exercise China's maritime administrative law enforcement jurisdiction, enhance deep-sea cruise enforcement and traffic control capabilities in key waters, ensure maritime traffic safety, and safeguard national rights and interests.”[xvi]

According to the State Council Taiwan Affairs Office spokesperson Zhu Fenglian, the special law enforcement operation “is a sovereignty declaration with both legal significance and political signaling,” confirming that “China has indisputable jurisdiction, law enforcement authority, and management rights over Taiwan and its surrounding waters.”[xvii] Should the talks continue, Japan and the Philippines will “face China’s resolute, direct, and forceful response”—continued provocations will lead to stronger countermeasures.[xviii] Taiwan and its surrounding waters are part of China; the special operation is intended to protect China’s core interests of “national sovereignty, security, and territorial integrity.”[xix]

There have been reports that CCG vessels have harassed merchant vessels passing through the region. CCG patrol ships, claiming jurisdiction over what they are calling China’s new coastal sea, have reportedly queried foreign-flagged vessels operating beyond the 12-nautical mile limit about their port of origin, ultimate destination, and details on their cargo. During the five-day operation, 198 vessels were hailed and queried in international waters, and a Chinese survey ship mapped the seabed east of Taiwan.[xx] CCG personnel reportedly issued three compliance corrections, “conducted patrols of key anchorages, marine construction zones, high-risk collision warning areas, and submarine cable corridors.”[xxi] Passing ships were additionally instructed to comply with navigation rules, and “vessel identification codes and navigational aid systems were checked throughout the operation.”[xxii]

A state-sanctioned commentary indicated that the law enforcement operation was intended to send three signals. First, the seabed mapping operation was the first by mainland China east of Taiwan, filling in the previously uncharted eastern flank of Taiwan’s coastal waters. Second, the enforcement action established a “coastal governance model” around Taiwan. Third, the terminology shift from Taiwan Strait to China’s “coastal waters,” the ocean where China is present, exercises jurisdiction, and governs.[xxiii]

Taiwan objected to the operation, calling it a provocative act and cognitive warfare, and warning that the Taiwan Navy would coordinate with the Taiwan Coast Guard Administration (CGA). The CGA deployed five ships to warn away CCG vessels, indicating that four Chinese vessels had been expelled from restricted waters.[xxiv] Additionally, CGA patrol vessels have advised passing merchant ships to ignore CCG inquiries.[xxv]

Similarly, the United States, Britain, France, and Germany expressed concerns over the special maritime law enforcement operation, indicating that CCG patrols east of Taiwan “threaten regional stability and freedom of navigation.”[xxvi] A U.S. State Department spokesperson indicated that China’s actions were “deeply destabilizing” and that the United States rejects “any assertion by China of authority to interfere with freedoms of navigation or overflight, the freedom to lay cables, or other lawful uses of the sea.”[xxvii] Similarly, in a separate (but rare) joint statement, the UK, France, and Germany indicated that China’s “actions threaten regional stability and the freedom of navigation and safety of international shipping.”[xxviii] The joint statement further reiterated that the UK, France, and Germany were opposed “to any unilateral change to the status quo, particularly by threat or use of force or coercion” and that it was “fundamental that all navigational rights and freedoms and the safety of seafarers and vessels are guaranteed and respected.”[xxix]

Concerns over the special maritime law enforcement operations were also raised in Canberra. Australian officials indicated that Australia has a clear interest in “peace and stability, unimpeded trade, and freedom of navigation.”[xxx] A spokesperson for the Department of Foreign Affairs and Trade reiterated that Australia is opposed to “any unilateral action to change the status quo across the Taiwan Strait” and encouraged “dialogue rather than coercion or the use of force.”[xxxi]

Law of Maritime Delimitation

UNCLOS requires that the delimitation of the EEZ between States with opposite or adjacent coasts shall be effected by agreement based on international law to achieve an equitable solution.[xxxii] If no agreement can be reached within a reasonable time, the States concerned shall resort to third-party dispute settlement. [xxxiii] Similarly, the delimitation of the continental shelf between States with opposite or adjacent coasts shall be effected by agreement based on international law to achieve an equitable solution.[xxxiv] If no agreement can be reached within a reasonable time, the States concerned shall resort to third-party dispute settlement.

China maintains that the Philippines and Japan are not adjacent to each other and have no overlapping EEZ claims east of Taiwan. Therefore, according to China, there is no maritime area between the two countries that requires delimitation.[xxxv] China’s position, however, is not correct. The Yonaguni and Hateruma Islands in Okinawa Prefecture are separated from Mavulis Island, the northern most of the Batanes Islands in the Philippines, by less than 400 nautical miles.[xxxvi] Therefore, contrary to China’s position, Japan and the Philippines do have overlapping EEZ claims east of Taiwan, which can be delimited by the parties.

Beijing additionally maintains that, because Taiwan is part of China, any boundary delimitation east of island requires China’s participation. Although any bilateral maritime boundary agreement that includes waters east of Taiwan would not be binding on China or Taiwan, there is nothing that prohibits Japan and the Philippines from negotiating such an agreement first, followed by negotiations with Taiwan in areas where the three nations’ EEZs overlap.[xxxvii] It is not uncommon for a bilateral agreement to reflect that it is without prejudice to third-party rights, and Japan has acknowledged that any bilateral agreement with the Philippines would not be legally binding on third parties.[xxxviii] International law is clear on this point—“a treaty does not create either obligations or rights for a third State without its consent.”[xxxix]

Moreover, from a national security perspective, a Japan-Philippines maritime boundary agreement reflects the deepening bilateral security and defense cooperation between the two nations. Such an agreement “would establish a clearer legal framework in the strategically important waters” along the first island chain.[xl] The boundary agreement would also clarify “jurisdiction over fisheries, law enforcement and coast guard operations” and would “complement allied coordination and maritime domain awareness in one of the Indo-Pacific’s most sensitive maritime corridors.”[xli]

Coastal State Authority in the Maritime Zones

All States may claim a 12-nm territorial sea, 24-nm contiguous zone, and 200-nm EEZ.[xlii] States exercise sovereignty over the territorial sea, subject to the right of innocent passage by foreign-flagged ships.[xliii] Coastal States may adopt laws and regulations relating to innocent passage in respect of:

1. safety of navigation and the regulation of maritime traffic;
2. the protection of navigational aids and facilities and other facilities or installations; (c) the protection of cables and pipelines;
3. the conservation of the living resources of the sea;
4. the prevention of infringement of the fisheries laws and regulations of the coastal State;
5. the preservation of the environment of the coastal State and the prevention, reduction and control of pollution thereof;
6. marine scientific research and hydrographic surveys; and
7. the prevention of infringement of the customs, fiscal, immigration or sanitary laws and regulations of the coastal State.[xliv]

Foreign ships exercising the right of innocent passage shall comply with these laws and regulations and all generally accepted international regulations relating to the prevention of collisions at sea (Collision Regulations).[xlv]

The coastal State may also take the necessary steps in its territorial sea to prevent passage that is not innocent. This includes the temporary suspension of innocent passage, without discrimination in form or in fact among foreign ships, in specified areas of the territorial sea if such suspension is essential for the protection of its security, including weapons exercises.[xlvi]

In the contiguous zone, coastal States may exercise the control necessary to: (a) prevent infringement of its customs, fiscal, immigration or sanitary laws and regulations within its territory or territorial sea; (b) punish infringement of the above laws and regulations committed within its territory or territorial sea.[xlvii]

Coastal State jurisdiction over foreign-flagged vessels in the EEZ, however, is limited to resource-related activities. In the EEZ, coastal States have “sovereign rights for the purpose of exploring and exploiting, conserving and managing the natural resources, whether living or non-living, of the waters superjacent to the seabed and of the seabed and its subsoil.”[xlviii] The coastal State additionally has jurisdiction over (1) the establishment and use of artificial islands, installations and structures; (2) marine scientific research (MSR); and (3) the protection and preservation of the marine environment.[xlix] These rights and duties will be exercised with “due regard” to the rights and duties of other States.[l]

There is no indication that China’s special maritime law enforcement operation was conducted within Taiwan’s claimed territorial sea. Rather, all indications are that the operation was carried out within what Taiwan’s 200-nautical mile EEZ and the high seas. Claiming that it has indisputable jurisdiction, law enforcement authority, and management rights over the “coastal waters” surrounding Taiwan is indefensible and does not change the fact that China’s authority over foreign-flagged vessels in these waters is severely limited, primarily to resource-related infractions.

Maritime Law Enforcement Operations in the EEZ and High Seas

As discussed above, coastal State jurisdiction over foreign-flagged vessels in the EEZ is limited to resource-related activities, regulation of MSR, and protection of the marine environment.[li] Thus, coastal States may take enforcement measures, for example, to prevent illegal fishing, to regulate MSR, and to protect the marine environment.

Coastal State environmental jurisdiction, however, is limited. If the coastal State has clear grounds to believe that a vessel navigating in the EEZ has, in the EEZ, committed a violation of the International Convention for the Prevention of Pollution from Ships (MARPOL) or coastal State laws and regulations giving effect to MARPOL, the coastal State may require the vessel to give information regarding its identity and port of registry, its last and its next port of call and other relevant information required to establish whether a violation has occurred.[lii]

Additionally, if the coastal State has clear grounds to believe that a vessel navigating in the EEZ has, in the EEZ, committed a violation of MARPOL that results in a “substantial discharge” causing or threatening “significant pollution” of the marine environment, the coastal State may undertake physical inspection of the vessel for matters relating to the violation if the vessel refuses to give information or if the information supplied by the vessel is manifestly at variance with the evident factual situation and if the circumstances of the case justify such inspection.[liii]

Finally, where there is clear objective evidence that a vessel navigating in the EEZ has, in the EEZ, committed a violation of MARPOL that results in a discharge causing “major damage” or threat of major damage to the coastline or related interests of the coastal State, or to any resources of the EEZ, that coastal State may, provided that the evidence so warrants, institute proceedings, including detention of the vessel, in accordance with its laws.

There are no indications that any of the foreign-flagged vessels queried or harassed by the CCG east of Taiwan were involved in any pollution-related event that would give China jurisdiction to intervene.

In the EEZ, the ships of all States enjoy high seas freedoms of navigation and overflight, the right to lay submarine cables and pipelines, and other internationally lawful uses of the sea.[liv] Similarly, the high seas are open to all States, which includes (inter alia): (1) freedom of navigation and overflight; (2) freedom to lay submarine cables and pipelines; (3) freedom of fishing; and (4) freedom of marine scientific research.[lv]

With limited exceptions, ships operating in the EEZ and the high seas are subject to the exclusive jurisdiction of the flag State.[lvi] A warship or other duly authorized government ship that encounters a foreign ship on the high seas is not justified in boarding it unless there is reasonable grounds for suspecting that (1) the ship is engage in piracy; (2) the ship is engaged in the slave trade; (3) the ship is engaged in unauthorized broadcasting; (4) the ship is without nationality; or (5) the ship is of the same nationality as the warship.[lvii] There are no indications that any of the foreign-flagged vessels encountered by the CCG east of Taiwan were engaged in any universal crime that would allow China to exercise law enforcement authority over these vessels.

Clearly, China’s special maritime law enforcement operation was not executed consistent with international law. CCG vessels participating in the operation lack legal authority to query and interfere with foreign-flagged vessels navigating in Taiwan’s EEZ and the high seas. These vessels enjoy unimpeded high seas freedoms in these waters and are (with limited exceptions not applicable here) subject to the exclusive jurisdiction of the flag State beyond the territorial sea. China’s purported law enforcement activities are an abuse of rights[lviii] and reflect the latest attempt to illegally gain greater control over ocean areas that are intended to be free and open for all States.

Conclusion

The international community must formally reject China’s threat to global commerce and its illegal assertion of jurisdiction over its so-called “coastal waters.” Such a zone does not exist and has no legal significance in international law. It is simply another ocean-grab effort by China to intimidate its neighbors and advance its illegal maritime claims in the waters surrounding Taiwan without adverse repercussions. Allowing China’s actions to go unchecked would be a serious breach of the first island chain and would encourage further Chinese aggression against Japan in the East China Sea and the Philippines in the South China Sea. Detering China now, by rejecting its absurd claims and coercive behavior, will cost less than responding to a full-scale inv