Last week the USS Lassen, a United States guided-missile destroyer, sailed within 12 nautical miles of a series of artificial islands built by China in the South China Sea. In response, China reportedly summoned the US Ambassador, with a state-run newspaper claiming that China was not afraid of fighting a war. China’s naval commander warned that the move was ‘dangerous and provocative’, and policy makers, officials and journalists on all sides of the dispute have debated the wisdom, or otherwise, of these actions by the US.

The latest move by the US comes in the wake of China’s actions in the previously uninhabited Spratly Island group. In late 2014, China began reclaiming land on a series of reefs, some of which were only partially exposed at low tide. In 2015, satellite images showed significant construction beginning on the reefs/islands. China based its claim over the reef/islands on the so-called ‘Nine-Dash Line’, a 1947 map drawn up by Chiang Kai-shek’s nationalist government. It has been used as the basis, once in 1958, and in 2009 before the UN, in order to substantiate China’s claims.

China’s claim has not gone uncontested. Both Vietnam and the Philippines lay claim to the Spratly Island group, and some of the islands fall within the Exclusive Economic Zone of Malaysia and Brunei under the United Nations Convention on the Law of the Sea (UNCLOS). The Philippines has brought a case challenging the validity of China’s claims before an arbitral tribunal under UNCLOS. Despite China’s argument that the is over competing sovereignty claims, and so outside the remit of the arbitral body, last week the Permanent Court of Arbitration rejected this argument and will consider the case under UNCLOS (see Lea Christopher’s piece on the ILA Reporter on 5 November 2015 summarising the tribunal’s decision). However, China has pre-empted any finding, stating that it will not comply with any unfavourable ruling.

The legal issues associated with the South China Sea are complicated. There is a distinction to be made between claims that are covered by customary law and claims that are covered by the international law of the sea (predominantly contained within UNCLOS). The case of the USS Lassen is to be distinguished on this basis as well, and Shannon Tiezzi’s Diplomat analysis is instructive on the point. The recent US patrol was not concerned with challenging China’s claim to sovereignty over the islands, but rather asserting freedom of navigation, a point which the author claims has been lost among much of the news coverage.

Under UNCLOS, territorial sea extends 12 nautical miles from the shore (article 3). Within it, any ship enjoys the right of innocent passage (article 19). The circumstances that will generate territorial sea is central to the current disputes. A key provision is article 13, regarding low-tide elevations (LTEs):

Where a low-tide elevation is wholly situated at a distance exceeding the breadth of the territorial sea from the mainland or an island, it has no territorial sea of its own.

Article 60 then states that artificial islands do not have any territorial sea of their own and are only entitled to at most a 500 metre ‘safety zone’. This means that under UNCLOS, any artificial structures built by China on LTEs have no territorial sea. Whilst some of China’s construction has occurred on land not considered LTEs, the US has only conducted patrols within 12 nm of Mischief and Subi reefs, artificial islands that were previously LTEs, and so understood by the US not to have a territorial sea. By asserting their right to freedom of navigation past such structures, Tiezzi suggests the US ‘is not challenging China’s sovereignty over the Spratly features; it is challenging the status of those features under international law‘.

With many other LTEs in the region, this stand on freedom of navigation past the Spratly chain is an important test. Understanding how patrols, such as the USS Lassen’s, challenge China under the international law of the sea will be central in understanding the broader geopolitical developments in the region.