New High Seas Treaty

China and Diplomacy

Will new High Seas Treaty open a fresh front-line in South China Sea disputes?

Effective January 17, the framework protects unique marine biodiversity and ecosystems in areas beyond any individual country’s jurisdiction

[Quote:]  The case has become a cornerstone for the Philippines in its territorial disputes with China and has been widely seen as a test of Beijing’s commitment to a rules-based international order.[End quote]

By Laura Zhou Published: 9:43am, 10 Feb 2026

https://www.scmp.com/news/china/diplomacy/article/3342892/will-new-high-seas-treaty-open-fresh-front-line-south-china-sea-disputes

Amid simmering tensions in the South China Sea, a likely new legal and diplomatic battlefield has emerged.

Two decades in the making, the High Seas Treaty, also known as the Biodiversity Beyond National Jurisdiction (BBNJ) agreement, took effect on January 17. That followed a key milestone reached last September, when 60 nations ratified the treaty – meeting the threshold for activation.

The BBNJ agreement is the most significant ocean treaty since the 1982 United Nations Convention on the Law of the Sea (Unclos).

It establishes a legally binding framework to protect the unique marine biodiversity and ecosystems of the high seas – areas that lie beyond the jurisdiction of any individual country.

The agreement also aims to create protected areas, stipulating that the global community should benefit equitably from the open oceans and their resources – including genetic material found in the high seas, a domain covering almost half of the world’s surface and more than 60 per cent of the global ocean.

But the focus of the High Seas Treaty is already shifting from biodiversity to boundaries.

By setting new global norms, the agreement could provide a rhetorical template for South China Sea claimants to mask territorial ambitions with the language of stewardship, turning conservation tools into a novel legal arsenal, analysts note.

Beijing actively advanced negotiations and signed the treaty when it opened at the UN in 2023. Two years later, last October, the National People’s Congress, China’s top legislature, formally ratified the agreement.

Last month, China surprised the world by announcing its bid to host the new treaty’s secretariat, a move seen as Beijing’s latest attempt to boost its sway in global discourse.

In China, officials and state media hailed the signing and ratification as evidence of Beijing’s commitment to be a responsible guardian and architect of global rules.

The events unfold against a backdrop of mounting challenges to the international order – from trade protectionism, apparent shifts in US foreign policy under its “America first” doctrine, and fiercer rivalries among great powers.

Washington signed the agreement during the Joe Biden administration, but it is unclear whether the current administration will ratify it, particularly given US President Donald Trump’s scepticism towards climate change and his interest in seabed mineral extraction.

Russia, another maritime power, has stated it will not take part in the BBNJ agreement, arguing the new treaty would undermine the high seas freedoms guaranteed by Unclos.

In contrast, Hua Chunying, China’s foreign vice-minister, told an international symposium in Beijing in December that Beijing’s decision to back the treaty would contribute to “effective implementation and universal participation in the agreement, injecting momentum into international governance of the deep sea and high seas”.

The BBNJ deal comes amid renewed tensions in the resource-rich South China Sea, where Beijing’s vast claims are contested by several Southeast Asian countries, including Vietnam, the Philippines, Malaysia and Brunei.

Frequent and aggressive confrontations between Chinese and Philippine coastguards in disputed waters over the past two years have heightened concerns that the region could become a dangerous hotspot, risking a wider conflict involving the United States, a long-time treaty ally of the Philippines.

While the BBNJ agreement neither grants new rights to claimants nor governs the settlement of disputes, analysts warn it could still open a fresh front for legal and diplomatic friction in the South China Sea.

The treaty could indirectly alter the strategic calculus as parties assess their interests, craft legal positions and design long-term strategies, according to Viet Hoang, an associate professor at the Ho Chi Minh City University of Law.

“The new legal norms introduced by the agreement have the potential to reshape the legal and strategic environment within which the South China Sea disputes are situated,” Hoang said.

The treaty allows for the creation of marine protected areas and other conservation measures to safeguard ocean life on the high seas, he added, noting that claimants might view these steps as indirect legal tools to challenge rival activities without directly tackling sovereignty issues.

Meanwhile, claimants might also seek to strengthen their legal standing by emphasising obligations relating to the conservation of marine biodiversity rather than engaging in direct confrontations over sovereignty, which have been sensitive and hard to reconcile.

“From a long-term strategic perspective, the BBNJ agreement may alter the ‘rules of the game’ in the South China Sea from power-based competition to norm-based competition,” according to Hoang, who is an expert on maritime law in Vietnam.

Hoang said that as international law increasingly incorporated values like sustainable development and environmental protection, countries “that proactively adapt to, domesticate and effectively implement the BBNJ agreement are likely to gain a comparative advantage in terms of credibility, influence and control over legal narratives in the South China Sea”.

For instance, in the Philippines, which ratified the treaty in September, there have been discussions to use the BBNJ agreement as a legal tool to bolster the country’s claims in the South China Sea by designating marine protected areas – a mechanism to restrict or even prohibit fishing and other commercial activities.

“We have high seas in the South China Sea. That’s a fact,” Antonio Carpio, a retired Philippine Supreme Court justice and vocal proponent of Manila’s claims in the disputed waters, told a forum in the Philippines in 2024.

“This High Seas Treaty is another layer, another legal instrument that would bury the 10-dash line of China,” he added, referring to Beijing’s territorial claims over nearly the whole of the South China Sea.

By invoking the BBNJ agreement in this manner, Manila could seek to consolidate its legal standing in the arbitration case it brought in 2013 over Beijing’s claims.

In 2016, in a direct blow to Beijing, an international tribunal at The Hague, constituted under Unclos, ruled in favour of the Philippines, invalidating China’s expansive claims to historic and economic rights.

Despite being a party to Unclos, China refused to take part in the tribunal, maintaining that the body had no jurisdiction over sovereignty disputes. China has also consistently rejected the ruling.

The case has become a cornerstone for the Philippines in its territorial disputes with China and has been widely seen as a test of Beijing’s commitment to a rules-based international order.

The US and its allies have argued that Beijing’s military activities, including its construction of fortified artificial islands in the South China Sea, undermine this order.

Shi Yubin, a professor at Zhejiang University and a specialist in the international law of the sea, said the South China Sea disputes and the 2016 arbitration ruling had been on the minds of Chinese negotiators.

Marine protected areas in the South China Sea are likely to be seen by Beijing as a challenge to its claims, according to Shi.

China considers the major island groups – such as the Spratlys, the Paracels and Zhongsha, including Scarborough Shoal – as part of its “indisputable sovereignty”.

China calls the Spratly Islands Nansha, the Paracels Xisha and Scarborough Shoal Huangyan Island.

To Beijing, no waters in the South China Sea should be declared high seas, Shi said.

[Photo caption] The marine protected areas mechanism will restrict or even prohibit fishing and other commercial activities. [Photo: Xinhua]

Beijing fought hard to ensure that the BBNJ agreement’s scope would not extend to disputed maritime areas.

According to Shi, who was involved in the treaty process, the BBNJ agreement includes an article intended to exclude disputed waters – such as those in the South China Sea – from being selected to establish marine protected areas.

That position is supported by other regional claimants, including the Philippines and Vietnam.

To avoid conservation measures possibly being misused or exploited to assert or challenge sovereignty, the agreement also states that international courts or tribunals under the framework have no jurisdiction over disputed waters.

Shi said the marine protected areas mentioned in the treaty were “very sensitive and have been a core concern” for China. Beijing had made it very clear that “no such areas should be applied to disputed waters”, primarily referring to the South China Sea, he added.

The observers noted that the BBNJ treaty’s pending implementation mechanisms could open a new front for dispute among rival claimants, particularly in light of the entrenched sovereignty conflicts in the South China Sea.

Hoang said this leeway could allow claimants to avoid open confrontation over sovereignty yet “still exert influence over legal outcomes”.

Mechanisms like marine protected areas could “be used to constrain or challenge the activities of other parties” without needing to address sovereignty explicitly, he added.

Shi cautioned about risks that the new treaty could become a tool for legal and political manoeuvring in South China Sea disputes, noting some of the BBNJ agreement’s provisions “could be subject to different interpretations”.

If Manila tried to establish a marine protected area in the South China Sea, Beijing would “mobilise all diplomatic efforts to resolve the issue”, he said.

Hoang said the new law would sharpen scrutiny of activities in the region and affect the strategic playbook of all territorial claimants, “particularly with regard to activities that may be perceived as posing risks to marine biological diversity”.

Under the BBNJ agreement, proposals for marine protected areas have to be submitted to the secretariat and then undergo rigorous review by a scientific and technical body.

Following a period of inclusive stakeholder consultation, the proposal would be presented to the conference of the parties (COP) – the treaty’s main decision-making body – for formal adoption.

Before the COP conference, which is expected to meet by the end of this year, two preparatory commissions were held in April and August last year.

The third and most crucial session is scheduled for March, when delegates will establish the rules and structures for the new agreement. This includes forming subsidiary committees such as the scientific and technical body that will review assessments and help to create marine protected areas.

China would defend its red line, Shi said, noting that territorial sovereignty was a “bottom line”.

Meanwhile, Vietnam, which presented its treaty ratification document to the UN in June last year, was expected to take a “cautious” approach to implementing the BBNJ agreement, to ensure that the newly established mechanisms “are not misused to legitimise unlawful claims or unilateral actions”, according to Hoang.

Carlyle Thayer, a Southeast Asia specialist and emeritus professor at the University of New South Wales, said the treaty could pave the way for littoral states to cooperate in creating a marine protected area without compromising their respective sovereignty.

As the 2026 chair of the Association of Southeast Asian Nations (Asean), the Philippines has said it might seek to fast-track negotiations and finally sign the South China Sea code of conduct (COC) – as committed by both China and Asean member states three years ago.

Negotiations on the China-Asean COC started in the early 2000s as a way to manage tensions in the strategically important waters. But little significant progress has been made, and deep divisions persist over its scope, definitions and enforcement.

Thayer said establishing marine protected areas under the BBNJ agreement could “easily be included in the [COC’s] single draft negotiating text if there is the political will to do so”.

However, he said prospects for doing so were “slim”, citing recent maritime confrontations between China and the Philippines.

In any case, “the opportunity to develop a marine protected area in the South China Sea is now on the table”, Thayer said.

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