For months, concern has been growing over China's aggressiveness in claiming a major portion of the South China Sea as its own lake, most recently through the deployment of a flotilla of some of its most modern warships into the Spratly archipelago on a three-week military exercise.

China has drawn a "U-shaped line" which encircles most of the South China Sea in an

arbitrary manner to delineate a claim whose nature and basis are not specified. It is a line that does not conform to any international law, including the United Nations Convention on the Law of the Sea of 1982. China has always avoided stating what kind of claim that line represents.

In the face of China's increasing assertiveness, US Secretary of State Hilary Clinton told the ASEAN regional forum in Hanoi last July that the United States "opposes the use or threat of force by any claimant. While the United States does not take sides on the competing territorial disputes over land features in the South China Sea, we believe claimants should pursue their territorial claims and the company and rights to maritime space in accordance with the UN convention on the law of the sea. Consistent with customary international law, legitimate claims to maritime space in the South China Sea should be derived solely from legitimate claims to land features."

Clinton's statement was consistent with international law, which forbids the use of force or threat of force to resolve disputes. It was also consistent with the the Law of the Sea, and with the US's longstanding policy of neutrality with regard to the sovereignty dispute over the Paracel Islands, the Spratly Islands and Scarborough Shoals. Furthermore, it is commendable that a country offers to facilitate discussions among the disputing parties.

Nevertheless, China has reacted angrily. China has always insisted that the South China Sea disputes be dealt with by way of bilateral negotiations and has developed a "two nos" policy regarding the South China Sea: no multilateral negotiations, no "internationalization." Therefore, in response to Clinton's statement, China attacked what it saw as the "internationalisation" of the South China Sea issue and argued that the disputes should be settled via bilateral negotiations.

Bilateral or Multilateral Disputes?

The issue consists of a number of separate disputes. The Paracels are claimed by China and Vietnam, the Scarborough Shoals by China and the Philippines and the Spratlys claimed in whole or in part by Brunei, China, Malaysia, the Philippines and Vietnam. There are also disputes over maritime zones, such as the exclusive economic zones and the extended continental shelves.

Last and perhaps most serious, China's "U-shaped line," which arbitrarily encircles most of the South China Sea, creates maritime disputes between it and Brunei, Malaysia, the Philippines, Vietnam, Indonesia, and potentially all countries in the world, all of which have rights in the South China Sea as granted by the UN convention.

Clearly, the dispute over the Paracels is a bilateral matter between China and Vietnam and should be resolved bilaterally between these two countries. If they are unable to reach agreement, China and Vietnam should seek mediation, as Indonesia and Malaysia did when these countries took their dispute over the Ligitan and Sipadan Islands to the International Court of Justice, or when Malaysia and Singapore did the same for their dispute over Pedra Branca/Pulau Batu Puteh, Middle Ledge and South Rocks.

Similarly, the dispute over Scarborough Shoals is a bilateral matter between China and the Philippines and should be solved in a similar manner.

The dispute over all or some of the Spratlys between Brunei, China, Malaysia, the Philippines and Vietnam is multilateral by definition. A multilateral dispute requires a multilateral solution. Bilateral negotiations are not an appropriate mechanism for resolving a multilateral dispute. A bilateral settlement between two of the claimants is unlikely to be acceptable to the remaining ones. For example, if the Philippines and Vietnam were to negotiate and settle bilaterally the sovereignty over the Spratly Islands, would China accept that as a solution?

The disputes over the maritime zones that might belong to the Spratlys are also multilateral and also require a multilateral solution involving all the claimants. Bilateral negotiations cannot offer a solution. So why does China insist on bilateral negotiations as the only mechanism to solve the disputes, despite the fact that this method could not be expected to bring about a resolution?

Clearly this is part of a divide-and-conquer strategy. China is hoping that its opponents will succumb one by one and accept less than equitable solutions.

Also, by insisting on an unsuitable approach, China is effectively blocking progress towards a negotiated settlement. As the strongest country in the disputes by far, the absence of peaceful settlements gives China increasing opportunities to strengthen its position and weaken those of the other claimants. Therefore, blocking progress towards a negotiated settlement by insisting on an unsuitable mechanism of negotiation works to China's advantage.

The Law of the Sea and China's "U-shaped line"

There are implications from the UN Convention on the Law of the Sea that make the disputes over the maritime areas in the South China Sea not just a matter concern to the claimants but one for all countries in the world.

China's "U-shaped line" lies far beyond the 12 nautical mile limit for sovereignty, far beyond legally likely limits for EEZ, and even beyond the equidistance line between the Spratlys, Paracels and opposite coasts.

The Convention, which has been ratified by 160 states – including China, stipulates that a coastal state only has sovereignty in the belt of territorial sea up to 12 nautical miles (22 km) wide adjacent to its baseline. Inside this territorial sea, the coastal state has full jurisdiction; other states have no rights except for that of "innocent passage," essentially a transit through the waters concerned for the purpose of getting elsewhere.

Beyond 12 nautical miles, the coastal state does not have sovereignty or full jurisdiction, but does have some specific rights granted by the law of the sea treaty such as exclusive economic rights in the exclusive economic zone, and exclusive rights to exploit the seabed and subsoil in the extended continental shelf.

This means that, roughly speaking, with only a 12-nautical-mile belt along the coastal baselines and around the Paracels, the Spratlys and the Scarborough Shoals can potentially be subjected to any state's sovereignty.

If a state claims it has sovereignty, as opposed to economic rights beyond these limits, it is in fact attempting to impose its full jurisdiction over waters where international law should be paramount. Therefore the international community has the right be concerned, and it would be in its interest to make its opposition clear.

Also, when a state makes an excessive EEZ claim, that claim is an encroachment either on the maritime zones belonging to its neighbours or on the high seas, where column of water and part of the seabed belong to the international community. The international community should be vigilant about and oppose any EEZ claim that encroaches unfairly on the high seas.

Would it be reasonable for the "U-shaped line" to represent a claim for an EEZ derived from the Paracel Islands and Spratly Islands? According to past rulings by the IJC and boundary treaties between states, even islands larger than the Spratlys and Paracels have been awarded EEZs or continental shelves that are barely more than 12 nautical miles wide. This would leave an area in the middle of the South China Sea as high seas. However, the "U-shaped line" lies massively beyond 12 nautical miles from the Paracel Islands and Spratly Islands and encroaches completely on this area.

Furthermore, international law and state practice never accord to an island an EEZ boundary that lies beyond the equidistant line between it and the opposite coasts that belong to larger islands or to continental land masses. However, not only does China's U-shaped line lie massively beyond 12 nautical miles, it also lies beyond any imaginable equidistant line.

Therefore, if the U-shaped line were to represent a claim for an EEZ derived from the Paracel Islands and Spratly Islands, that claim would be an excessive one and it would encroach completely on an area that might well be high seas – not to mention the fact that the disputed islands do not necessarily belong to China.

Additionally, China's narrow view of the freedom of navigation in what it sees as its EEZ, as exemplified by the incident in which Chinese ships harassed the US surveillance ship Impeccable, makes any excessive EEZ claim by China even more problematic for the international community in general and for its South China Sea neighbours in particular. Would it be reasonable for the U-shaped line to represent a claim for a continental shelf based on the natural prolongation of land territories into the seabed?

Due to Vietnam's long coastline and the Sunda Shelf extending from the south of the South China Sea, the application of the principle of natural prolongation and UNCLOS would give Vietnam, Malaysia and the Philippines most of the continental shelves in the South China Sea.

Therefore, the U-shaped line cannot be reasonably be justified by application of the principle of natural prolongation of land territories into the seabed.

It is noteworthy that in the East China Sea, China uses the principle of natural prolongation to claim the entire continental shelf extending from its mainland coast to the continental margin at the Okinawa Trough, and yet in the South China Sea, China opposes to Vietnam and Malaysia applying this principle.

Another inconsistency in China's claims is that while China's continental shelf claim in the East China Sea would leave Japan's Ryukyu Islands with maritime zones that fall far short of the equidistance line, the U-shaped line would give the disputed Paracel Islands and maritime zones that extend beyond the equidistance line.

China therefore faces a choice of either abandoning its U-shaped line in order to conform to the Law of the Sea or maintaining it against all internationally accepted rules and precedents. Unfortunately, it seems to be going down the second route. In recent years, China has passed a law that outlaws any map which does not depict the U-shaped line. In 2009, it submitted a map with the U-shaped line to the UN for the first time. All indications are that China is trying to ratchet up its U-shaped line claim while being opaque on the nature and basis of the claim.

Since the U-shaped line cannot be justified as an exclusive economic zone or continental shelf claim derived from the Paracel Islands and Spratly Islands, some Chinese scholars have tried to justify it using the argument of historic title over maritime space. However, a claim derived from the argument of historic title over maritime space is not a claim to maritime space derived from land feature, and is therefore not in accordance with the Law of the Sea. This might explain partly why China felt so targeted when Clinton made her statement that claimants should pursue their territorial claims in accordance with the UN convention on the law of the sea.

Of serious concern, claims of historic titles and historic waters can imply claims of sovereignty and given China's opaqueness on the matter, it cannot be ruled out that China is claiming, or one day might claim, sovereignty beyond 12 nautical miles.

In short, China's U-shaped line is either an excessive EEZ claim, or an unjustifiable continental shelf claim, or an excessive sovereignty claim – none of which can be justified as being derived from the Paracel Islands and Spratly Islands within the framework of the Law of the Sea.

Internationalisation or De-internationalization?

Given that the Law of the Sea defines the rights of all countries in all the seas and oceans and has been ratified by 160 states, including China, the international community should oppose the U-shaped line in whatever form. While the international community can afford to remain neutral on the question of sovereignty over the Paracels, the Spratlys and the Scarborough Shoals, it cannot afford to be neutral about the U-shaped line.

Throughout history, the South China Sea has always been an international sea, just as the Mediterranean. According to the Law of the Sea, the littoral states have sovereignty out to a distance of 12 nautical miles from the coasts and the islands. The rest, which is most of the South China Sea, is subject to international law and the Law of the Sea. This means that most of the South China Sea remains international, just as the Mediterranean, and the international community has the the right to take an interest in the maritime claims there.

China's opposition to the "internationalisation" of the South China Sea issue is tantamount to an attempt to de-internationalise an international sea. Once the South China Sea has been de-internationalised, China will be able to bring its strength to bear on the Southeast Asian countries and impose its own rules, rather than internationally accepted ones from international law on these waters. This will turn the South China Sea into a Chinese lake, with serious consequences for both Southeast Asia and the rest of the international community.

Huy Duong, PhD, is an IT consultant living in the UK. He contributes articles on the South China Sea to several news outlets including the BBC and Vietnam's online publication VietNamNet. Tinh Le, PhD, is a nuclear engineer living in France.