Recently, controversy has arisen over China’s installation of floating structures in the Provisional Measures Zone (PMZ) under the South Korea-China Fisheries Agreement. This article aims to ascertain the facts of the incident and draw its implications under international law.

 
Summary of the Incident
 
Currently, there are two Chinese offshore floating structures in the West Sea (Yellow Sea), named Shenlan No. 1 and Shenlan No. 2. Shenlan No. 1 was installed on July 2, 2018, and Shenlan No. 2 is estimated to have been installed in May 2024. These structures are located within the PMZ under the South Korea-China Fisheries Agreement, in waters closer to the Chinese side of the imaginary median line that could serve as the EEZ delimitation line between the two countries. Shenlan No. 1 has a diameter of 60m and a height of 35m, while Shenlan No. 2 is larger, with a diameter of 70m and a height of 71.5m. China claims that these structures are deep-sea aquaculture facilities. However, in South Korea, there is suspicion that these structures are a strategic move to assert effective control over the West Sea (Yellow Sea).

On February 26, 2025, when the South Korean marine research vessel Onnuriho attempted to inspect the structures and approached within 1km of them, the Chinese Coast Guard and civilians prevented the deployment of research equipment. In response, the South Korean Coast Guard also dispatched a vessel to the scene and confronted the Chinese vessels. Subsequently, at the South Korea-China foreign ministers’ meeting, South Korea expressed concern about the infringement of its legitimate maritime rights, and China responded that it would continue communication.

 
Are the Installations of the Structures in Violation of International Law?
 
To determine whether China’s installation of structures in the West Sea (Yellow Sea) violates international law, we will examine the South Korea-China Fisheries Agreement and the United Nations Convention on the Law of the Sea (UNCLOS).

1) Violation of the South Korea-China Fisheries Agreement: Not Likely

The installation of the structures itself is difficult to view as a violation of the South Korea-China Fisheries Agreement. The agreement only regulates fishing activities in the West Sea (Yellow Sea) and does not explicitly prohibit the installation of structures. However, if the installation of structures harms the safety of navigation and fishing operations or adversely affects marine biological resources, a violation of the agreement may arise. In this case, the issue can be raised through the South Korea-China Joint Fisheries Committee, and China may be urged to take appropriate measures.

2) Violation of the United Nations Convention on the Law of the Sea: Likely

UNCLOS stipulates regulations regarding Exclusive Economic Zones (EEZs), but since the EEZ delimitation between South Korea and China has not been established, those regulations cannot be applied as is in waters where the EEZ claims of both countries overlap. However, UNCLOS clearly states that artificial islands, facilities, and structures do not have the status of islands and do not affect the delimitation of territorial waters, EEZs, or continental shelves. Therefore, China cannot declare an EEZ based on the existence of these structures.

The important question is whether China’s act of installing structures in the West Sea (Yellow Sea) violates the “obligation of self-restraint” under UNCLOS, which means the obligation “not to jeopardize or hamper the reaching of the final agreement” (UNCLOS Article 74(3)). Since Shenlan No. 1 and Shenland No. 2 are installed on the west side of the median line¾often used as the baseline for EEZ delimitation between the two countries¾the fact that this area may eventually be recognized as part of China’s EEZ after formal delimitation makes it difficult to judge whether the obligation of self-restraint has been violated. However, if the installation of structures is carried out continuously, repeatedly, and cumulatively, and results in the infringement of South Korea’s sovereign rights¾such as interference with fishing activities, destruction of the marine environment, or a reduction in marine biological resources¾it may be viewed as a violation of this obligation of self-restraint.

In addition, UNCLOS stipulates an obligation to protect the marine environment and to conduct environmental impact assessments. It is currently unknown what impact China’s installation of structures in the West Sea (Yellow Sea) has on the surrounding marine environment. It is therefore necessary to verify whether China conducted an environmental impact assessment, particularly in light of the possibility that aquaculture farming may cause substantial pollution or harmful changes to the marine environment and fish resources. If such an assessment was not conducted, the South Korean government could claim that China has violated UNCLOS regulations.

Furthermore, UNCLOS recognizes the right to conduct marine scientific research to all member states. On February 26, the Onnuriho research vessel attempted to measure the potential environmental impact of the Chinese structures in the West Sea (Yellow Sea), but it was unable to conduct its planned survey due to Chinese interference. This constitutes an infringement of South Korea’s right to conduct marine scientific research under UNCLOS.

 
South Korea’s Responses
 
China’s act of installing structures in the West Sea (Yellow Sea) does not in itself constitute a violation of either the South Korea-China Fisheries Agreement or UNCLOS regulations. Therefore, excessive responses should be avoided. However, if these structures negatively impact the maintenance of fishing order or the preservation of marine biological resources, they may violate the purpose and spirit of the South Korea-China Fisheries Agreement and the duty to prevent harm, which is considered a general principle of international law. Moreover, if the installation of structures is carried out continuously, cumulatively, and repeatedly, it may violate the obligation of self-restraint under UNCLOS.

Therefore, South Korea must continue to pursue the following responses:

• Protest through diplomatic channels regarding the possibility that China’s actions infringe on South Korea’s legitimate maritime rights under UNCLOS.

• Discuss the impact of the structures on maintaining fishing order in the PMZ and the state of marine biological resources through the South Korea-China Joint Fisheries Committee and seek solutions.

• Demand that the Chinese government conduct an environmental impact assessment and disclose the findings publicly.

• If China continues to act irresponsibly, consider filing a lawsuit with the International Tribunal for the Law of the Sea (ITLOS). In this case, a litigation strategy must be established to avoid China’s declaration of exclusion of compulsory jurisdiction.

• Urge China to engage sincerely in EEZ delimitation talks with South Korea.

• Consider entrusting the EEZ delimitation issue to an authoritative international judicial body-such as the ITLOS or the International Court of Justice (ICJ)-based on mutual agreement. Filing a delimitation case before the ICJ through the conclusion of a special agreement under Article 36(1) of the ICJ Statute may be an appropriate option.