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China's South China Sea claims are audacious, which is why The Hague's decision is huge

If the reefs in the South China Sea had a consciousness of their own, they'd probably be pretty flattered by all the attention international experts in maritime law are paying to them now.

When is a reef just a reef? Is a reef still a reef, if somebody comes along, dredges up tons of coral and sand, and starts layering the stuff on top of it? What if it doesn't stop at just reclamation? What if they lay air-strips, carve out ports? Is it still a reef? Or is it an island now?

What should be a existential issue left to the reefs themselves has become a set of legal questions with answers that could have huge implications for international relations.

That's because these questions form the basis of the Philippines' legal challenge to China's claim over almost all of the South China Sea.

It's clever, even cheeky, on the part of Manila, which asked The Hague to clarify whether submerged or partially-submerged physical features in the South China Sea can be claimed by any country.

Under the UN's Convention on the Law of the Sea (UNCLOS), submerged or partially-submerged features (and which can't support human life) cannot be claimed by any country, which is entirely entirely reasonable. Why would any country want to claim ownership or sovereignty over rocks poking out of the sea that serve no useful human purpose?

So, Manila's asking The Hague to confirm that UNCLOS definition, by asking, "Are you sure that, legally, this definition is right?".

If The Hague says that it is, then the question is then whether the definition still applies to the several reefs that China's built up (experts think not coincidentally over the past three years since Manila lodged its case with The Hague) into instant but artificial islands.

Whether the UNCLOS definition also applies to man-made islands is something The Hague will also decide. And this bit is key. Because if the United Nations' court rules that they are islands, then they come with what's called a 200 nautical-mile "exclusive economic zone" (EEZ) around them.

In other words, the sovereignty over these islands for whichever country claims them extends much further out into the sea than the features themselves.

Why is this important? Because China's done the math, taken out its calipers and sextants, and made sure the features they've built into islands (and their EEZs) form a loose patchwork quilt in the sea that defines almost unbroken ownership of the entire South China Sea.

So the headline is, this is about access - in, out, and through the South China Sea - but it's also about extreme economic leverage.

EEZs come with fishing and mineral (read: oil) rights. Imagine the handful of other Southeast Asian countries that have competing claims over the South China Sea asking China, "How about this bit here, then?". To which China repeatedly replies, "Nope, that's mine too."

Even the fish in the sea and the untapped oil under the seabed.

What China is in effect doing is almost audacious beyond belief.

But ... if the UN rules that the features China's built into islands are not, actually, islands, then China's claims totally fall apart.

We'll know by 5:00 p.m. HK/SIN. That's just before lunch in the Netherlands, when The Hague's decision is expected. It will be complex, not binary.

Regardless of the ruling, what won't change is the reality that all of China's built structures won't go away anytime soon. Satellite images have shown at least three military grade and length airstrips, plenty of buildings, as well as deep-water port facilities.

The kicker is that images also show much more mundane things, such as running tracks and basketball courts. Looks like China's in this for the long haul.

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