The International Tribunal for the Law of the Sea has made a definitive ruling on one of the world's most dangerous disputes: China's claim to the South China Sea.

It is ocean far to the south of China, lying between Vietnam and the Philippines, which calls it the West Philippine Sea.

The competing claims were of little interest to the rest of the world until China began turning some of the ocean's remote rocks and reefs into concrete islands with air strips, possibly for a military purpose.

China made no secret of its intention to assert territorial sovereignty and maritime rights over an area containing vital sea lanes and resources of value.

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The tribunal at the Hague has been considering a case brought against China by the Philippines more than three years ago.

Its ruling this week does not resolve the competing claims to the Spratley Islands and other disputed rocks, but it states most clearly that these tiny and largely artificial creations far from China's coast do not entitle China to claim maritime rights under the Law of the Sea.

China refused to participate in the case and does not recognise it as a legitimate exercise under international law. The court at the Hague has no way to enforce its rulings, of course, but a country that refuses to abide by a ruling at international law can hardly claim the rights and benefits awarded by that law.

China cannot assert an exclusive economic zone out to a 200 mile (370km) radius of its new marine outposts if it refuses to recognise the authority of the very law that created the possibility of an exclusive economic zone.

China's claim to an ocean surrounded by Southeast Asia is a concern not just to the region, it is seen in Washington and other Western capitals as evidence that China has ambitions to be expansionary military superpower.

That suspicion was reinforced by an article supplied to the Herald by China's embassy in Wellington last month, which we published on June 15.

It saw the US Government's declared "Asia-Pacific rebalancing" in 2010 as a provocation of China and it interpreted the Philippines' application to the Hague tribunal in that light.

Noting the application to the Hague was made in January 2013, and China's island building started at the end of that year, the article in the name of the ambassador stated, "The scale and speed of China's reef construction matched the international responsibilities and obligations assumed by China as a major power."

The long tongue of territory that China claims in the South China Sea looks outrageous to neighbouring countries and to the rest of the word, but by all accounts of those who know China, it is absolutely taken for granted within that country, regarded as part of China from time immemorial.

So far it has made no threat to the passage of shipping on a trade route that is vital to China.

New Zealand foreign policy has not taken sides in the latest dispute. So long as international law is observed and sea lanes remain open, trade probably will be a reliable influence for peace.