The South China Sea Dispute: What International Law Actually Says, What's at Stake for Shipping, and Why It Matters Now

A map shared widely on social media this week captured a reality that 500,000 merchant vessel transits per year depend on: China claims sovereign rights over waters nearly 1,000 kilometers from its nearest coastline, directly overlapping the exclusive economic zones of the Philippines, Vietnam, Malaysia, Brunei, and Indonesia. The post, viewed over 227,000 times, called China a bully. But the South China Sea dispute is not a matter of opinion. International law has already rendered its verdict. The question is whether that verdict matters.

THE LEGAL FACTS

On 12 July 2016, the Permanent Court of Arbitration in The Hague issued a landmark ruling in the case brought by the Philippines against China (PCA Case No. 2013-19). The tribunal ruled overwhelmingly in the Philippines' favor on nearly every submission.

The key findings were unambiguous. First, China's nine-dash line claim — the sweeping boundary that encompasses roughly 90 percent of the South China Sea — has no legal basis under the United Nations Convention on the Law of the Sea (UNCLOS). The tribunal stated that to the extent China had historic rights to resources within the sea areas of the nine-dash line, those rights were extinguished by UNCLOS when China ratified the convention in 1996. There was no legal basis for China to claim historic rights to resources within these maritime areas.

Second, none of the Spratly Islands features claimed by China are capable of generating an exclusive economic zone. The tribunal examined every major feature and determined that Mischief Reef, Second Thomas Shoal, and others are either low-tide elevations or rocks incapable of sustaining human habitation, meaning they generate no EEZ under UNCLOS Article 121. This is significant because it means even if China had sovereignty over these features, it could not legally claim the surrounding 200 nautical miles of ocean.

Third, China violated Philippine sovereign rights by interfering with fishing and petroleum exploration at Reed Bank, by constructing artificial islands, and by failing to protect the marine environment through massive dredging and reef destruction. The tribunal found that China's island-building had caused severe, irreversible harm to the coral reef ecosystem.

China refused to participate in the proceedings and has refused to recognize the ruling, calling it "null and void." Ten years later, it remains the most significant unimplemented ruling in modern international maritime law.

CHINA'S POSITION

China's claims rest on what it describes as historical rights predating modern international law. Beijing argues that Chinese navigators and fishermen have used the South China Sea for over 2,000 years, and that the nine-dash line (originally an eleven-dash line drawn by the Republic of China in 1947) reflects longstanding sovereignty.

However, international legal scholars and historians have challenged this narrative. Bill Hayton of Chatham House documented that as late as 1899, Qing dynasty officials denied responsibility for the Paracel Islands in an insurance dispute, and as late as 1933, senior officials of the Republic of China were unaware of the existence of the Spratly Islands. The US Naval Institute's Proceedings journal concluded in August 2024 that the historical evidence behind China's claims is "insufficient and untenable."

China's embassy in Manila stated in March 2026 that China "has never laid claim" to the entirety of the South China Sea as its territory — a statement the Philippines immediately rejected, pointing to the nine-dash line map that China itself submits to the United Nations as evidence of its claims.

THE MILITARY REALITY ON THE GROUND — AND WATER

Whatever the law says, China has created facts on the water. Between 2013 and 2016, China constructed approximately 3,200 acres of artificial land across seven reef sites in the Spratly Islands. These artificial islands now host military-grade airstrips, radar installations, anti-ship missile batteries, and naval facilities. The Center for Strategic and International Studies (CSIS) documented in February 2026 that China continued expanding coast guard deployments and island construction throughout 2025.

The China Coast Guard (CCG) doubled its presence at Scarborough Shoal in 2025 and nearly tripled patrols around Sabina Shoal. In October 2025, CCG vessels used high-pressure water cannons against Filipino fishing craft at Thitu Island and Sabina Shoal. In February 2026, the CCG confiscated fish aggregating devices deployed by Filipino fishermen near Scarborough Shoal, claiming they posed navigation and ecological hazards.

In March 2026, the Philippine Coast Guard deployed vessels to protect Filipino fishermen at Bajo de Masinloc (Scarborough Shoal) and Escoda Shoal after fresh reports of harassment by Chinese maritime militia and CCG vessels.

Meanwhile, the United States deepened military engagement with the Philippines, which in turn prompted reciprocal Chinese naval deployments — a classic security dilemma spiral.

WHAT'S ACTUALLY AT STAKE

The South China Sea is not abstract geopolitics. It is the single most important commercial shipping corridor on Earth.

An estimated $3.4 trillion worth of goods transit the South China Sea annually — roughly one-third of global maritime trade. Approximately 500,000 merchant vessel transits occur each year. The waterway connects Northeast Asia's manufacturing powerhouses (China, Japan, South Korea, Taiwan) to the energy supplies of the Middle East and the consumer markets of Europe. Every barrel of oil bound for Japan or South Korea passes through these waters. Every container from Shenzhen to Rotterdam passes through these waters.

The US Energy Information Administration estimates the South China Sea holds approximately 11 billion barrels of proved and probable oil reserves and 190 trillion cubic feet of natural gas. The US Geological Survey estimated an additional 12 billion barrels of undiscovered oil and 160 trillion cubic feet of undiscovered gas. Control over these resources is a primary driver of the competing claims.

THE MARITIME INDUSTRY IMPACT

For the shipping industry, the South China Sea dispute creates three categories of risk.

First, navigational safety. The CCG's aggressive behavior toward civilian vessels — water cannons, ramming, blocking — creates direct hazards for merchant shipping in the area. While most incidents have targeted Philippine government and fishing vessels, the precedent of a coast guard willing to use force against civilian craft in disputed waters is alarming for commercial operators.

Second, insurance exposure. If tensions escalate to the point where the Lloyd's Joint War Committee designates South China Sea waters as a listed area — as it has done for the Red Sea and now Hormuz — the insurance cost impact on global trade would dwarf any previous maritime crisis. A JWC listing would add war risk premiums to every vessel transiting Asia's primary trade route. Given that the South China Sea handles roughly ten times the trade volume of the Strait of Hormuz, the economic consequences would be unprecedented.

Third, rerouting risk. If commercial shipping is forced to avoid the South China Sea — as vessels have been forced to avoid the Red Sea — alternative routes through the Lombok or Makassar Straits would add 2 to 5 days to Asia-Europe transit times, increase fuel consumption, and strain already-pressured global supply chains. Deutsche Welle reported that rerouting from Red Sea disruptions alone caused significant cost spikes. A South China Sea disruption would amplify those effects by an order of magnitude.

THE UNCOMFORTABLE TRUTH

The post that went viral gets the geography right. China is claiming sovereign interests over waters that are 1,000 kilometers from its mainland and directly adjacent to the Philippines. International law, through the highest available tribunal, has ruled those claims have no legal basis.

But the uncomfortable truth is that international law without enforcement is aspiration, not reality. China has nuclear weapons, the world's largest navy by hull count, and permanent membership on the UN Security Council. No mechanism exists to compel compliance with the PCA ruling. The Philippines, Vietnam, and other claimant states lack the military capacity to enforce the ruling independently.

What does exist is economic interdependence. China itself depends on South China Sea shipping lanes for its own imports of energy and raw materials. Any disruption to free navigation would hurt China as much as its neighbors. This mutual vulnerability is, paradoxically, the strongest guarantee of continued commercial passage — for now.

For the maritime industry, the South China Sea dispute is not a crisis today. But it is the highest-consequence risk on the horizon. If the Hormuz crisis has taught the shipping world anything, it is that chokepoints become crises faster than anyone predicts. The South China Sea is the world's most important chokepoint. The law is clear. The enforcement is not. And 500,000 ships per year sail through the gap between the two.

Sources: Permanent Court of Arbitration (PCA Case No. 2013-19, Award of 12 July 2016), UNCLOS Articles 56 and 121, US-China Economic and Security Review Commission, CSIS Asia Maritime Transparency Initiative, CSIS ChinaPower Project, US Energy Information Administration, US Geological Survey, US Naval Institute Proceedings (August 2024), Council on Geostrategy (Bill Hayton research), East Asia Forum (February 2026), Reuters (March 2026), Manila Bulletin (March 2026), Xinhua (March 2026), Deutsche Welle, Allianz Commercial marine risk analysis, CIMSEC.