The 2016 South China Sea Ruling at Nine: Where Does ASEAN Stand?

Almost nine years ago on 12 July 2016, an arbitral tribunal constituted under Annex VII of the 1982 United Nations Convention on Law of the Sea (UNCLOS) delivered a landmark ruling on the Philippines’ 2013 case against China in the South China Sea (SCS). Scholars, regional and international, praised the decision as a legal milestone for clarifying key issues, including rejecting China’s so-called ‘nine-dash-line’, invalidating China’s historic rights claims, and defining the maritime entitlements of features in the disputed Spratly Islands. (Editor’s note: “Maritime entitlements” typically refer to what nation-states can claim under UNCLOS as their territorial seas, exclusive economic zones (EEZs), and continental shelves.)

While the ruling helped to narrow the areas of dispute, its impact on the region remains contested. Tensions continue to escalate in the disputed SCS, with frequent confrontations between Chinese vessels – military and commercial – and those of Indonesia, Malaysia, Vietnam, and the Philippines. Meanwhile, ASEAN has struggled to present a united front. Observers have widely criticised ASEAN’s failure to issue a joint statement after the ruling and its ongoing exclusion of the case from relevant official documents on regional maritime affairs as evidence of the bloc’s fragmentation in addressing the SCS dispute.

Still, there are signs of a quiet shift. Recent developments suggest that, despite their differences, ASEAN member states (AMS) may be converging toward a shared understanding grounded in international law, particularly UNCLOS, acknowledging the legal validity of the 2016 ruling.

First, the relevant ASEAN countries neighbouring the SCS have publicly rejected China’s core claims within its ‘nine-dash-line’. Indonesia (a non-claimant whose Natunas islands are a source of bilateral dispute and tension with China) and SCS claimant Malaysia explicitly reject the legal basis of China’s historic rights claims in the Sea. In its note verbale to the United Nations, Indonesia cited the 2016 arbitral ruling, reinforcing its alignment with the legal conclusions set out by the tribunal. Likewise, Vietnam rejects all (of China’s) maritime claims in the SCS that go beyond the limits set out by UNCLOS, including historic rights claims.

Regarding the legal status of maritime features in the disputed Spratlys, Indonesia, Malaysia, and Vietnam have reaffirmed their commitment to UNCLOS in determining offshore features’ maritime entitlements, supporting the 2016 tribunal’s finding that none of the Spratlys’ features can generate an EEZ or continental shelf. Even Brunei, typically a more reticent SCS claimant, has emphasised the primacy of international law, particularly UNCLOS, on this issue. (Under Article 121 UNCLOS, only geographic features recognised as “islands” can generate or support maritime zones like territorial seas, et cetera. In the 2013-2016 case, the Philippines disputed China’s interpretation and application of A.121 to the SCS. The tribunal found in favour of the Philippines’ position.)

By confirming that each maritime feature in the SCS should be treated individually, these AMS’ statements implicitly reject using China’s preferred tactic of drawing straight baselines around offshore maritime features to claim maritime zones. China’s approach – criticised by many, including Chinese legal scholars, as excessive – to drawing such baselines around its claimed offshore island groups in the SCS, such as the Paracels and Scarborough Shoal, has been firmly challenged by Vietnam and the Philippines, with Indonesia and Malaysia echoing their stance. Notably, these countries articulated their legal arguments in a note verbale to the United Nations, consistent with the reasoning of the 2016 ruling, reinforcing their shared support for the award.

Taken together, these developments highlight the impact of the 2016 award in shaping the legal and geopolitical practices of ASEAN countries.

The Philippines formally incorporated the 2016 ruling into its domestic law, signalling its strongest commitment to uphold the award and the law of the sea.

This growing alignment among some AMS suggests the emergence of a more unified front on the SCS, which quietly affirms the decisions of the 2016 ruling and rejects any state’s unilateral assertions of maritime dominance. More importantly, certain AMS have used the 2016 ruling as a legal basis to challenge China’s excessive claims in the SCS, allowing them to frame their positions with greater clarity, consistency, and legitimacy.

The positions of non-claimant AMS other than Indonesia are also worth noting. For example, Singapore and Myanmar have acknowledged the significance of the ruling. While Singapore emphasises peaceful dispute resolution and adherence to international law, Myanmar has endorsed a rules-based maritime order.

Importantly, the SCS issue has made its way into ASEAN’s highest-level policy documents. While earlier texts like the ASEAN Maritime Outlook acknowledged its significance through general statements, grouped with other strategic maritime areas such as the Straits of Malacca, ASEAN 2045: Our Shared Future, adopted in 2025, arguably marks a shift in ASEAN’s approach. Here, the South China Sea is identified as a strategic goal, with ASEAN explicitly supporting not only diplomatic engagement but also the effective implementation of UNCLOS, including the use of legal processes to resolve disputes.

Given that ASEAN decision-making is by consensus, the inclusion of the SCS as a standalone issue and a strong commitment to international law, particularly UNCLOS, in recent documents and statements, suggests agreement – even from typically reserved members like Cambodia, Laos, and Thailand – towards a rules-based maritime order in the SCS. In this emerging consensus, the relevance of the 2016 ruling is clear.

Taken together, these developments highlight the impact of the 2016 award in shaping the legal and geopolitical practices of ASEAN countries. In their ongoing legal exchanges (mainly via notes verbale) with China, relevant AMS, which are SCS claimants, have frequently anchored their positions following the legal reasoning set forth in the award, turning it into a powerful tool in the region’s legal diplomacy. As a result, the award has subtly steered those countries toward a collective stance. Setting aside the protracted negotiations on the SCS Code of Conduct with China, ASEAN as a bloc shows signs of moving toward more coherence in ocean governance by reinforcing the centrality of UNCLOS as “the legal framework within which all activities in the oceans and seas must be carried out” and embracing a rules-based framework.

*The views expressed in this article are the author’s own and do not reflect those of her affiliated institution.

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