When I began researching South China Sea issues, the topic was often the butt of deprecating jokes from ‘global strategic thinkers’ because they thought the issues were ‘inconsequential’. A common comment was ‘sea level rise will solve all the problems there, ‘ implying that the sea will cover all the contested features and thus make the disputes over ownership irrelevant. Such banality woefully underestimated the significance and complexity of these territorial and jurisdictional conundrums. We now know that these disputes could spark serious kinetic conflict. And instead of disputed features in the Spratlys becoming submerged, the reverse has now happened. A new natural feature –Sandy Cay–has appeared, and become the focus of a dangerous standoff over its ownership.
Sandy Cay is actually three coalescing sand bars situated between Philippines -occupied Thitu (Pag-asa) and China-occupied Subi. They are now above water at high tide. Thus they are legal ‘rocks’ which according to the UN Convention on the Law of the Sea (UNCLOS) entitles them to a 12 nautical mile (nm) territorial sea. A territorial sea is the sovereign territory of a state and this sovereignty extends to the airspace above and the seabed below and of course the associated resources.
Given the sweeping claims to parts of the South China Sea, ordinarily a dispute over the ownership of a sandbar would not be a big deal. But it so happens that the sovereign of these sandbars would significantly enhance its strategic and legal position in the area. This probably underlies the recent tiff between the Philippines and China. China appears to be trying to protect its sovereignty claim over Sandy Cay. https://www.foxnews.com/us/us-envoy-says-china-activities-near-philippines-of-concern
Indeed, according to the Philippines Ambassador to China, Chito Sta. Romano, China is “watching Sandy Cay”. https://www.rappler.com/newsbreak/in-depth/229034-dissecting-duterte-amped-up-west-philippine-sea-rhetoric
The current contretemps arose in January 2019 when a swarm of about 275 Chinese vessels appeared near Thitu beginning in January 2019. The Philippines declared that the presence of the vessels violated its “sovereignty, sovereign rights, and jurisdiction”. Many thought this swarm was a response to the Philippines construction on Thitu. It may have started out that way, but the focus is now on Sandy Cay and the issue has become much more complicated.
Thitu is an above high tide feature. This means that it also is a legal rock entitled to a 12 nm territorial sea. China claims and occupies Subi Reef – about 16 nm to the west. Subi is a low tide feature not entitled to a territorial sea. Indeed it is not legal “territory” and cannot be claimed as such by any nation.
The Philippines position is that China’s sovereignty claim to Subi is invalid and that it lies within the Philippines EEZ and on its continental shelf. But Subi also lies within the 12 nm territorial sea of Sandy Cay. Both China and the Philippines claim these sandbars – outright as their sovereign territory– and indirectly because they are situated within Thitu’s 12 nm territorial sea. Since both claim Thitu and its territorial sea they believe they have the right to both fish there and to exclude the other’s fishers.
If China were the sovereign of either Thitu or Sandy Cay, or both, it would validate both its claim and occupation of Subi. Also, if China gains sovereignty over these sandbars, the median line between the sandbars would then be the theoretical legal boundary. In that case, the Philippines would lose much of its claimed territorial sea to the west of Thitu https://globalnation.inquirer.net/174189/analyst-china-maritime-militia-near-pag-asa-threatens-ph-sea-air-access . The claimants may try to enforce their respective claims in the territorial waters each claims.
China has reason to be concerned about possible aggressive Philippine actions regarding Sandy Cay. In 2017, the Philippines began to build fishermen’s shelters on these sandbars. China objected and Chinese fishing boats formed a ‘blockade’ to prevent access of Philippine fishermen to Sandy Cay, and from fishing in what it considers its territorial waters emanating from it. It cited the nonbinding 2002 ASEAN-China Declaration of the Conduct of Parties in the South China Sea (DOC) that forbids “inhabiting on the presently uninhabited islands, reef, shoals, cays _ _ _.” https://asean.org/?static_post=declaration-on-the-conduct-of-parties-in-the-south-china-sea-2 Philippines President Rodrigo Duterte ordered the shelters to be dismantled and the construction to stop. In the present situation, China may have feared that the Philippines was about to do something similar again.