South China Sea, explained.
Satellite image of Fiery Cross Reef with a large artificial island, runway, harbour basin, dense building clusters, and surrounding reef flats (2026 Vantor via Getty Images)
As ASEAN builds new maritime institutions, it keeps leaving its strongest legal instrument off the table.
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Ten years on, can ASEAN finally put the South China Sea ruling to work?Ten years on, can ASEAN finally put the South China Sea ruling to work?
As maritime coercion in the South China Sea becomes ever more routine, Southeast Asian governments have focused on managing tensions while continuing to underutilise one of the region’s most potent legal instruments.
A decade after the landmark 2016 South China Sea Arbitration Award (Opens in new window) invalidated China’s “nine-dash line” claims and affirmed the Philippines’ sovereign rights within its exclusive economic zone, ASEAN claimant states have struggled to translate this legal victory into an effective foundation for maritime diplomacy. The tribunal could never force China to comply. But the ruling’s enduring value lies in providing a common framework that ASEAN states could invoke to reinforce the rules-based maritime order.
The award’s most unrealised value lies not in compelling compliance, but in shaping ASEAN’s collective diplomatic strategy. It has remained more symbolic than operational and had only minimal influence on ASEAN’s collective approach to the South China Sea.
The 2016 South China Sea Arbitration Award clarified the application of the United Nations Convention on the Law of the Sea (UNCLOS) in the South China Sea and established an authoritative legal baseline for maritime claims. China rejected the ruling outright (Opens in new window) and continued to expand its presence in disputed waters. The Philippines under Rodrigo Duterte largely set the Award aside (Opens in new window) in favour of closer ties with Beijing. ASEAN, meanwhile, prioritised dialogue through Code of Conduct negotiations (Opens in new window), and other claimant states, including Vietnam and Malaysia, rarely placed the Award at the centre of their diplomacy.
The arbitration’s limited influence reflects ASEAN’s broader approach to the South China Sea over the past decade. Confronted with China’s growing assertiveness, Southeast Asian governments have reasonably prioritised crisis management over legal advocacy. China has also demonstrated its willingness to impose diplomatic and economic costs on states that challenge its position.
Hearing in session, 7 July 2015, at the Permanent Court of Arbitration at The Hague (PCA)
ASEAN’s consensus-based decision-making also makes the adoption of strong legal language challenging amid differing economic priorities and varying degrees of involvement in the disputes. Under these circumstances, the failure of the arbitration to become the focal point of ASEAN’s regional strategy was predictable.
But this does not diminish its potential value. Rather than being viewed as an alternative to diplomacy, the ruling provides a shared legal baseline upon which ASEAN claimant states can coordinate their diplomacy, reinforce UNCLOS, and strengthen their collective position.
The regional context has shifted. Under the Philippines’ 2026 ASEAN chairmanship, Manila has sought to conclude a legally binding Code of Conduct (Opens in new window) by the end of the year through an accelerated schedule of ASEAN–China negotiations while insisting that the agreement be firmly anchored in UNCLOS. At the same time, ASEAN leaders endorsed the establishment of the ASEAN Maritime Centre (Opens in new window) in the Philippines to strengthen regional maritime cooperation and governance. These developments represent ASEAN’s most consequential investment in maritime cooperation in years.
But the ASEAN Leaders’ Declaration on Maritime Cooperation (Opens in new window) makes no reference to the 2016 South China Sea Arbitration Award, despite repeatedly reaffirming UNCLOS as the legal framework governing maritime activities in the region. This omission is striking given the Philippines’ efforts to anchor the Code of Conduct in UNCLOS while strengthening ASEAN’s institutions through the ASEAN Maritime Centre.
The award's most unrealised value lies not in compelling compliance, but in shaping ASEAN’s collective diplomatic strategy.
Reaffirming UNCLOS without reference to the Arbitration Award leaves ASEAN without a common legal point of reference for interpreting how the Convention applies to the South China Sea. This leaves member states free to articulate their maritime positions from differing legal and diplomatic perspectives, ultimately limiting ASEAN’s ability to present a coherent and consistent regional position despite its growing institutional cooperation.
Placing greater emphasis on the Arbitration Award would not automatically lead to regional tensions. Rather, it can be viewed as a practical tool that complements ASEAN’s existing diplomatic approach. The ASEAN Maritime Centre offers the chance to incorporate the Award into legal and maritime capacity-building, while ASEAN could draw more consistently upon its findings in joint statements and future discussions surrounding the Code of Conduct.
None of these measures require China’s acceptance of the ruling; Beijing’s position is already well established. Instead, putting the Award at the centre could strengthen ASEAN’s own legal coherence and provide a more consistent legal foundation for its expanding maritime cooperation.
About the author
Maxine Nazaree Co
Maxine Nazaree Co’s research focuses on maritime security, ASEAN, and foreign policy in the Asia-Pacific, with a particular interest in the South China Sea.
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