China, explained.
A Vietnamese Coast Guard ship is challenged by a China Coast Guard ship near to the site of a Chinese oil drilling rig being installed in disputed waters in the South China Sea (Hoang Dinh Nam/Getty Images)
All sides would benefit if they stopped insisting that only their sovereignty is indivisible while everyone else’s is negotiable.
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South China Sea: Competing sovereignty is sinking joint developmentSouth China Sea: Competing sovereignty is sinking joint development
A decade after an international tribunal (Opens in new window) nullified the legal basis for China’s sovereignty claim over the South China Sea (the “nine-dash line”), discussion about joint development is back. In March, Philippine President Ferdinand Marcos Jr called the dispute over who has legal claim over the South China Sea an “impetus (Opens in new window)” for restarting joint oil and gas talks with China. Officials met in Quanzhou, with Beijing declaring its door open if Manila would “demonstrate sincerity (Opens in new window)”. Jakarta moved earlier — the November 2024 joint statement by presidents Xi Jinping and Prabowo Subianto recorded a common understanding on “joint development in areas of overlapping claims (Opens in new window)”.
Joint development will work not when the region finds the right formula, but when both sides mean the same thing by sovereignty.
Yet every previous attempt at joint development has collapsed. The puzzle is why the idea keeps returning, and why it keeps failing.
The answer lies less in geopolitics than in a dispute over the definition of sovereignty. One tradition treats it as indivisible – incapable of being shared without being lost. Another (Opens in new window) treats it as a bundle of rights that can be divided and renegotiated. The UN Convention on the Law of the Sea (UNCLOS (Opens in new window)) is drafted according to this second logic, separating sovereignty from sovereign rights and jurisdiction, and inviting provisional arrangements “without prejudice” to final settlement of disputes. Joint development lives inside this second world.
That is why then Philippines President Gloria Macapagal Arroyo could present the 2005 Joint Marine Seismic Undertaking with China and Vietnam – much of it inside the Philippines’ exclusive economic zone – as sovereignty-neutral. It was “just a research survey (Opens in new window)” that left every legal position untouched. Cooperation, on this reading, spent no sovereignty.
The Philippine Supreme Court read the same episode differently. In January 2023 it declared the undertaking unconstitutional (Opens in new window), holding that even “pre-exploration” surveying was exploration of the national patrimony, and that joint ownership of the data deprived the state of the “full control and supervision” which the 1987 Constitution demands. The 2018 (Opens in new window) memorandum with Beijing, signed during Xi Jinping’s visit to Manila to frame joint oil and gas development without prejudice to sovereignty, had already failed on similar grounds: terminating the talks in 2022, then foreign secretary Teodoro Locsin said (Opens in new window) negotiations had gone as far as constitutionally possible – resources would not be developed at the price of sovereignty.
Herein lies the trap. The only type of arrangement that satisfies Manila – a service contract under full Philippine control, anchored (Opens in new window) in the 2016 tribunal decision – is one that requires Beijing to accept a ruling it rejects. The clarity of that ruling has closed the ambiguity that once made joint development feasible. For the Marcos administration, negotiating (Opens in new window) jointly with China over Reed Bank (Opens in new window) gas development – an energy-rich area within the Philippines’ exclusive economic zone – risks reviving a claim the tribunal extinguished.
Beijing’s formula asks others to treat their sovereign rights as divisible while presenting its own nine-dash claim as indivisible.
Nor can President Marcos unbundle Philippines’ sovereignty by decree. The 2016 tribunal ruling is now embedded in Philippine law through the 2024 Maritime Zones Act (Opens in new window), enforced by courts, agencies and a public that has internalised its indivisibility.
Jakarta is running the same experiment. For a decade, Indonesia insisted it had no overlapping claims with China. President Prabowo Subianto’s Beijing statement appeared (Opens in new window) to concede otherwise before officials clarified that China’s claims “have no international legal basis (Opens in new window)”. Jakarta faces an identical dilemma. Each capital can lawfully cooperate only on terms that negate Beijing’s conception of sovereignty, and Beijing will cooperate only on terms that negate theirs. The same dilemma extends beyond bilateral dynamics, as Jakarta revives (Opens in new window) the Tuna Block project with a Russian state-owned firm (Opens in new window), with Beijing notably holding back from earlier protests.
The newest test is the UN Biodiversity Beyond National Jurisdiction Agreement, in force (Opens in new window) since January 2026. The treaty embodies the same “divisible” view of sovereignty as UNCLOS – Article 18 (Opens in new window) provides that high-seas marine protected areas “shall not be relied upon as a basis for asserting or denying any claims” to sovereignty. The agreement applies only beyond national jurisdiction, but in the South China Sea that boundary is itself disputed, meaning the treaty cannot be applied without first taking a position it was meant to avoid. An instrument designed to set sovereignty aside cannot define its own scope without resolving the dispute it was supposed to side-step.
The instruments that have worked in the South China Sea point the way. The region’s environmental cooperation (Opens in new window) has succeeded by insulating itself from sovereignty disputes: funds are held by an external trustee, disbursements are tied to ecological targets, and scientists rather than foreign ministers are in the lead.
To translate this success to resource cooperation, three design rules should be observed. First, structure ventures within national jurisdiction: the coastal state’s law governs the venture and foreign firms enter as service contractors, taking a share of production but never a share of rights. Second, keep sovereignty vocabulary out of the text altogether – a clause never written cannot be litigated; define project areas by geographic coordinates, not names or other characterisations; and put the agreement or project documents in the hands of a neutral third party. Third, sequence: prove the model on fisheries and marine protection projects first, where insulated precedents already exist, before tackling hydrocarbon projects carrying the greatest political weight.
None of this secures Chinese consent. Beijing’s formula – set aside disputes, pursue joint development (Opens in new window) – asks others to treat their sovereign rights as divisible while presenting its own nine-dash claim as indivisible. Joint development becomes possible only when China applies the same flexibility to its own claims.
Until then, the task in Manila and Jakarta is as much defensive as creative: cooperate where mechanisms can be insulated. Joint development will work not when the region finds the right formula, but when both sides mean the same thing by sovereignty.
About the author
Emirza Adi Syailendra
Emirza Syailendra is a Postdoctoral Research Fellow at the Maritime Security Programme, S.
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