China is taking the highly unusual step of refusing to participate in a United Nations arbitration process over a territorial conflict with the Philippines, one of five countries challenging Beijing’s claims of ownership over the oil-rich South China Sea.

The legal dispute underscores the tough geopolitical approach China is adopting in the Pacific region. It has adopted an aggressive approach toward neighbours over a 2,000-mile stretch that also includes the East China Sea, over which it recently declared the air defence identification zone that has inflamed tensions with Japan and South Korea.

China sent its only aircraft carrier to the disputed waters off the coast of the Philippines for the first time last week, in a move Manila said raised tensions. China’s military said the carrier Liaoning will conduct drills in the area, accompanied by two destroyers and two frigates.

Dealing with the fallout over China’s territorial claims has become the dominant issue for the US vice-president, Joe Biden, who is currently touring the Asia Pacific region.

Biden arrived in South Korea on Thursday after high-level bilateral meetings in China and Japan that were dominated by the issue of the air defence zone.

The Philippines will submit its formal case to the UN arbitration tribunal of judges, which has agreed to hear the case at The Hague, in March. A preview of their arguments were outlined this week in Washington by Paul Reichler, an expert attorney at Foley Hoag LLP hired by Manila to handle the case.

He said China’s blank refusal to participate in the tribunal process, a move it revealed to the Philippines by way of diplomatic letter in February, marked the first time a state had ever refused to take part in an inter-state arbitration under the 1982 UN Convention on the Law of the Sea.

Under the convention, the panel of senior international judges is still required to issue a ruling in the case, despite China’s non-cooperation, although Reichler conceded there were no way of enforcing any ruling.

But he added: “There is a price to be paid for branding yourself an international outlaw – a state that does not comply with the rules.” China declined an opportunity to comment on the case.

The dispute concerns China’s declaration of the so-called nine-dash line, which claims jurisdiction over nearly all of the mineral-rich South China Sea, overlapping with large segments of territory claimed by the Philippines as well as of Vietnam, Malaysia, Brunei and Taiwan.

In parts, China’s declared jurisdiction, which enables it to exploit lucrative fishing waters and potential oil and gas reserves, stretch more than 800 miles from its mainland coast. It also comes to within 30 miles of the coast of the Philippines.

Under the convention, states have a right to an exclusive economic zone and continental shelf within 200 miles of their coast. Disputes over the South China Sea are not unlike those over the Japanese-administered Senkaku islands – referred to as the Diaoyu islands in China – which are dominating Biden’s visits to Japan, China and South Korea this week.

Although the ad-hoc tribunal formed to deal with the case cannot rule on the sovereignty of the islands claimed by both China and the Philippines, it can provide rulings about the nature of rock formations, with implications for any territorial claims under the convention. Some of the disputed territories are barely visible at high tide, while others are fully submerged even at low tide.

In a bid to strengthen its claims, China has constructed concrete installations on some underwater formations, complete with basketballs and helipads. “A state cannot transform an underwater feature into an island by building on top of it,” Reichler said at a seminar organised by the Center for Strategic and International Studies.

In simple terms, the judges will in part be asked to determine when a rock can be defined as an island. If a rock protruding from the sea cannot sustain human life or economic activity, for example, the associated rights in surrounding waters are, under the convention, dramatically reduced, regardless of which state claims ownership.

Reichler also showed one slideshow of an island that, at high-tide, consisted of rocks that only just protruded out of the water. “It is barely big enough to support the Filipino flag,” he said.