China’s recent unilateral decision to prohibit navigation around artificial structures within the Provisional Measures Zone (PMZ) in the West Sea is far more than a routine maritime restriction. It is a calculated move that undermines the principles of international maritime law and poses a strategic threat to the balance of power in Northeast Asia. We must not regard this as a mere fisheries dispute or a limited maritime conflict. What is unfolding in the West Sea is part of a broader gray zone strategy that seeks to silently revise the rules of the sea and erode South Korea’s maritime sovereignty.

The United Nations Convention on the Law of the Sea (UNCLOS) clearly guarantees the freedom of navigation in Exclusive Economic Zones (EEZs) through Article 58, while Article 60 stipulates that artificial structures shall not affect territorial seas or maritime boundaries. Yet, China is ignoring these provisions, restricting navigation based on its installations-an act that amounts to an illegal territorial expansion by stealth. This behavior also violates Article 74, which prohibits actions that might influence maritime boundary negotiations prior to their conclusion.

On the environmental front, China has failed to conduct the required Environmental Impact Assessment (EIA) before constructing these facilities. Its physical obstruction of a Korean survey vessel in February is a direct breach of Article 206 of UNCLOS. Moreover, these actions contravene the spirit and stipulations of the 2000 Korea-China Fisheries Agreement, which strictly limits non-fishing activities in the PMZ and permits each state to exercise jurisdiction only over its own vessels. China’s implied enforcement against foreign ships undermines the fundamental principle of flag-state jurisdiction upon which the agreement is based.

The implications extend well beyond legal violations. China’s recent construction of three large structures-“Shenlan 1 & 2” and a converted drilling platform, each measuring over 70 meters in diameter-suggests far more than civilian intent. These structures are situated in a strategically sensitive zone that includes key South Korean security assets such as the Pyeongtaek U.S. base, the Jeju naval base, and the Ieodo Ocean Research Station. This is not an accident. It reflects a deliberate strategy to extend China’s maritime reach and military influence. China appears to be replicating its successful “salami-slicing” tactics from the South China Sea, aiming to establish a de facto presence that shifts the status quo in its favor.

Recent incidents reinforce this interpretation. In March, a Chinese tourist was caught photographing sensitive military facilities in South Korea-a potential act of coordinated intelligence gathering. This is no longer a matter of maritime jurisdiction alone. It is an intersection of intelligence operations, maritime militarization, legal circumvention, and geopolitical strategy.

So how should South Korea respond? A legal response is essential, but the timing and intensity must be carefully calibrated. An immediate lawsuit filed with the International Tribunal for the Law of the Sea (ITLOS) may not be optimal, given the complex interdependencies in Korea-China relations. Instead, the first step must be to raise international awareness and rally diplomatic pressure. South Korea should engage legal experts, international law associations such as the International Law Association (ILA), and organizations like the International Maritime Organization (IMO) to publicize China’s violations and build global consensus.

If such efforts fail to deter continued Chinese expansion, legal escalation must remain on the table. The precedent set by the Philippines’ 2016 arbitration ruling against China provides a powerful legal foundation for action. The ruling proved that unilateral actions in contested waters can be challenged and delegitimized under international law. South Korea should prepare to do the same.

Simultaneously, we must strengthen our surveillance and situational awareness capabilities. The Ministry of Oceans and Fisheries’ recent deployment of observation buoys in the PMZ is a welcome development. But we must go further-regularize these deployments, integrate satellite surveillance, and enhance real-time maritime intelligence-sharing with key partners like the United States. This is the backbone of effective maritime domain awareness.

Ultimately, however, South Korea must confront China’s so-called “West Sea Project” with a comprehensive maritime strategy of its own. The sea is no longer merely a source of fish or energy. It is a political space where security, sovereignty, and strategy converge. Maritime sovereignty is becoming more contested and vulnerable than even our land borders. If we fail to act, our waters may be quietly lost without a single shot fired.

The time for silence is over. What is at stake is not only South Korea’s sovereign rights at sea, but the integrity of the international maritime order in Northeast Asia. We must speak firmly, act strategically, and lead decisively.