The arbitration award issued in The Republic of the Philippines v. The People's Republic of China reaches its tenth anniversary this year, and commentators are once again assessing what the ruling has meant for international maritime law.

The case, decided on 12 July 2016, came before an arbitral tribunal constituted under Annex VII of the United Nations Convention on the Law of the Sea (UNCLOS). The Permanent Court of Arbitration in The Hague served as registry for the proceedings. The Philippines initiated the arbitration in 2013 after years of escalating friction with Beijing over contested features and waters in the South China Sea.

The tribunal ruled decisively for the Philippines on the core submissions. It held that China's so-called nine-dash line claim — the sweeping demarcation enclosing most of the South China Sea — had no legal basis under UNCLOS. The award also classified the disputed features in the Spratly Islands group, finding that none of them qualified as full islands generating entitlement to a 200-nautical-mile exclusive economic zone. At most, the tribunal concluded, they were rocks entitled only to a 12-nautical-mile territorial sea, or low-tide elevations generating no entitlements of their own.

The tribunal further found that China had, through actions such as island-building and interference with Philippine fishing and petroleum activities, breached its obligations under the Convention, including duties to protect the marine environment.

China refused to participate in the proceedings and rejected the award outright. Beijing declared the ruling "null and void" and "a piece of waste paper," insisting it would neither accept nor recognise it. That position has not changed in the decade since. The award, however, is final and binding under Article 296 of UNCLOS, and no appeal mechanism exists.

Why does a decade-old ruling that the respondent state refuses to implement still matter? The answer lies in what the award did for the law itself.

First, the decision gave the international community an authoritative interpretation of maritime entitlements under UNCLOS. By rejecting historic rights claims that exceed the Convention's framework, the tribunal reinforced that UNCLOS — not vague assertions of historic usage — governs entitlements to maritime space. States drafting submissions, negotiating maritime boundaries, or advising clients on offshore energy and fisheries interests now work against the backdrop of that clarification.

Second, the tribunal's article-by-article analysis of what constitutes an "island" under Article 121(3) of UNCLOS — capable of sustaining human habitation or economic life of its own — remains the most detailed judicial treatment of that provision to date. Practitioners advising on competing claims involving small features, from the Pacific to the Eastern Mediterranean, cite the award routinely.

Third, the case confirmed that jurisdiction under UNCLOS's compulsory dispute-settlement machinery can operate even when one party declines to appear. The tribunal made formal findings on jurisdiction, applying the customary rules reflected in Article 288, before reaching the merits. That procedural precedent has shaped subsequent state practice and the confidence of smaller states in invoking Annex VII arbitration.

The practical consequences on the water have been messier. China has continued to press its claims through coast guard presence, maritime militia activity, and artificial-island construction. Confrontations between Chinese vessels and Philippine ships near Second Thomas Shoal and Scarborough Shoal have intensified in recent years. The Philippines has responded by publicising incidents, invoking the 2016 award in diplomatic protests, and deepening security cooperation with treaty ally the United States and other partners.

Yet even states wary of antagonising Beijing have quietly anchored their positions in the award's reasoning. When tensions flare, governments from Southeast Asia and beyond routinely reference the 2016 ruling as "final and legally binding." That formula, repeated across a decade of joint statements and summit declarations, reflects the award's enduring authority even where enforcement is absent.

For legal practitioners, the tenth anniversary is a reminder of both the strength and the limits of adversarial adjudication in maritime disputes. The award clarified the law and strengthened the hand of a weaker claimant in the court of world opinion. It did not, and could not, compel a great power to change its behaviour at sea.

The tribunal's legacy therefore sits in two registers. In the courtroom and the treaty text, its holdings on maritime entitlements, island status, and historic rights are settled law, cited and applied. In the South China Sea itself, the contest continues — carried out by ships, dredgers, and press releases rather than pleadings.

Ten years on, the award stands as the clearest judicial statement of the rules that govern one of the world's most contested bodies of water. Whether those rules will govern conduct there as firmly as they govern doctrine remains the open question of the next decade.