2025.05.30

China’s Installment of Buoys in the East China Sea from an International Law Perspective

Editor's Note:
This column was submitted on May 26, two days before the Japan Coast Guard’s announcement of China’s removal of the remaining buoy in Japan’s EEZ near Yonaguni Island.
Accordingly, no China’s buoys are reported to be placed in Japan’s EEZ at the moment.
Japan Coast Guard’s announcement: (*1)

In recent years, Chinese buoys were spotted in a row in Japan’s exclusive economic zone (EEZ) near the Senkaku Islands (in July 2023 (*2)) and Yonaguni Island (in December 2024(*3)), on the Japan side of the geographical equidistance line between Japan and China in the East China Sea—the presence of similar buoys was also confirmed by the Japanese government in 2016 and 2018 respectively—. The news media (*4) reported that they were believed to be equipped with automatic identification systems (AIS) and a complex array of cameras, sensors, antennas, satellite transponders and other devices possibly for collecting and transmitting data on foreign vessels’ movements, water temperature, ocean currents,weather, etc. The Japanese government have issued a navigational warning to all vessels operating in the area, and strongly and repeatedly urged China to remove them immediately,arguing that the installment of the buoys is a unilateral attempt to change the status quo in the East China Sea. On February 11, 2025, the Chinese government made an announcement that one near the Senkaku Islands was relocated due to the completion of its task on the spot, commenting that its installment was consistent with both domestic and international laws. The Japan Coast Guard confirmed (*5) the removal of the buoy from Japan’s EEZ on the same day, but another buoy in the vicinity of Yonaguni Island is left as it is (*6).

In the meantime, the Japanese government has stated on various occasions that it would implement feasible and effective responses to China’s installment of the buoys in light of the rights and obligations of the countries concerned in the relevant waters, Japanese laws and regulations, and their potential impact on ship traffic and Japan’s fishing activities.
Domestically, however, there remains a strong argument that since the buoy remains located within its EEZ, Japan, as a coastal state, should take a resolute stance by removing the buoy on its own. Yet, is such a forcible removal permissible under international law at all? If so, under what circumstances, will it be legally justified?

To answer these questions, it must be emphasized that the installation of buoys by China within Japan’s EEZ could constitute the violations of the relevant rules of the law of the sea.
First, the installation could violate Article 246(2) of the United Nations Convention on the Law of the Sea (UNCLOS) which provides: “Marine scientific research in the exclusive economic zone and on the continental shelf shall be conducted with the consent of the coastal State.”
Insofar as the installation is, or was, for the purpose of marine scientific research (MSR), its unilateral act without Japan’s consent would not be consistent with the said article.

On the other hand, the EEZ and the continental shelf in the East China Sea, where the installation of the buoys is in question, have not yet been delimited. The official position (*7) of the Japanese government is that “the geographical equidistance line is regarded as an equitable solution in the delimitation of such maritime area.” By contrast, China refuses (*8) final delimitation based on the equidistance line and instead claims the natural prolongation of its continental shelf to the Okinawa Trough. Despite no mention of the boundary delimitation of the EEZ, China may thus refute the Japanese allegation of violation of Article 246(2) of the UNCLOS by claiming that the buoys have been located within China’s EEZ.

However, it must be recalled that the self-restraint obligation (*9) under the law of the sea comes into play in undelimited maritime areas. Article 74(3) of the UNCLOS stipulates that “the States concerned, in a spirit of understanding and cooperation, shall make every effort to enter into provisional arrangements of a practical nature and, during this transitional period, not to jeopardize or hamper the reaching of the final agreement” for the delimitation (underline added). As part of this effort, Japan and China established in 2001 a mutual advance notification framework for marine research activities (*10) as a temporary arrangement, under which China should notify Japan in advance when conducting MSR in Japan’s EEZ in the East China Sea. Nevertheless, the fact that China unilaterally installed its buoys without prior notification arguably disrespects this framework and, more importantly, demonstrates China’s failure to comply with its self-restraint obligation for reaching the final agreement on the boundary delimitation, whether for MSR purposes or not.　The breach of this obligation has been further aggravated by the acceleration of its development activities of natural resources in the East China Sea (*11).

Every breach of an international obligation attributable to a state entails the responsibility of that state (Articles 1 and 2 of the Articles of State Responsibility (*12)). The responsible state is under the obligations to cease the act of breach and make full reparation for the injury caused by it (Articles 30 and 31). When the breach continues, the injured state is
entitled to take proportionate countermeasures against the responsible state by resorting to illegal conduct in an effort to induce to comply with those obligations on the specified conditions (Articles 22, 51 and 52). Therefore, even if its forcible removal of the Chinese buoy were to cause any violations of international law, including that of China’s sovereign immunity, Japan could justify its act of removal based on its right to take countermeasures —all the more so because it has repeatedly called upon China to fulfill the relevant international obligations. It goes without saying, but for Japan to avoid breaching its obligation of self-restraint in undelimited maritime areas through disproportionate countermeasures, it is important that its self-help measures be limited to the removal of the buoy, and that Japan should immediately return it and, as the injured state, seek guarantees of non-repetition, while demonstrating its intention to continue making every effort to achieve a peaceful resolution for the maritime delimitation in the East China Sea. This de-escalatory form of countermeasures is consistent with their object and limits, notably “such a way as to permit the resumption of performance of the obligations in question” (Article 49).

It is up to the Japanese government whether to exercise the right to take countermeasures. The reason that Japan has thus far refrained from forcibly removing the buoys is probably because it has not confirmed any serious damages caused to Japan’s EEZ by their installation. However, should such damages become apparent in the future, it will be critical for Japan to take a resolute approach to forcible removal in order to protect its own maritime rights and interests.
(The opinions expressed here are solely those of the author and do not necessarily represent the position of the Japanese government or the Ministry of Defense of Japan.)

Notes:

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China’s Installment of Buoys in the East China Sea from an International Law Perspective

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