The Philippines’ Legal Offensive and the Evolving Lawfare in the South China Sea: Anticipating International Legal Pathways and China’s Strategic Responses

In recent years, the Philippines has spearheaded an ongoing legal offensive against China in the South China Sea, supported by various non-regional powers. Its use of international legal means to achieve political and strategic objectives has become a defining feature of the geopolitical dynamics in the South China Sea region. The Philippines’ actions, which seek to challenge China’s territorial claims and maritime rights through international legal mechanisms, are part of a broader strategy aimed at pressuring China within the so-called “rules-based international maritime order”. This commentary explores the potential international legal pathways the Philippines and other South China Sea claimant States may pursue to challenge China’s claims, while also examining how China might respond to these legal challenges. By understanding the trajectory of this lawfare, China can better anticipate future legal challenges and adopt strategies to safeguard its territorial integrity and maritime interests.

I. The Philippines’ Legal Offensive: Three Possible International Legal Pathways

The Philippines’ legal offensive in the South China Sea has been centered around utilizing international legal mechanisms to challenge China’s maritime claims and territorial sovereignty, especially in the Spratly Islands (Nansha Qundao) and Scarborough Shoal (Huangyan Dao). The key platforms available for such challenges include the International Court of Justice (ICJ), the International Tribunal for the Law of the Sea (ITLOS), and arbitration under Annex VII of the United Nations Convention on the Law of the Sea (UNCLOS).

First of all, the International Court of Justice (ICJ), as the principal judicial body of the United Nations, holds considerable legal authority in resolving disputes between States. However, the jurisdiction of the ICJ is strictly based on State consent, which China has never granted. Accordingly, China’s categorical refusal to accept any of the ICJ’s jurisdiction precludes any direct contentious cases against China at the Court. Despite this, the Philippines may still be able to utilize the ICJ’s advisory jurisdiction based on Article 96 of the UN Charter and Article 65 of the ICJ Statute, which allows UN organs or specialized agencies to request advisory opinions on critical legal questions. While China’s veto power as a permanent member of the UN Security Council could block any such initiative within the Security Council, a broader mobilization within the UN General Assembly might provide the Philippines an alternative route for obtaining an advisory opinion on issues related to the South China Sea. This strategy would closely mirror the legal battle over the Chagos Archipelago, where Mauritius successfully pushed for a UNGA-backed advisory opinion against the United Kingdom in 2019. Indeed, in January 2025, Gregory Poling, Director of the Asia Maritime Transparency Initiative (AMTI), suggested that the Philippines, with the support of the United States and its allies, should mobilize support in the UN General Assembly to initiate an advisory opinion procedure through a General Assembly resolution.

Secondly, the International Tribunal for the Law of the Sea (ITLOS), with its specialized focus on international law of the sea, presents a similar challenge. Although China’s generally non-acceptance to ITLOS jurisdiction limits direct contentious proceedings, ITLOS has increasingly issued advisory opinions, particularly related to maritime disputes and environmental issues. Article 21 of the Statute of ITLOS defines the Tribunal’s jurisdiction to include all disputes and applications submitted to it under the UNCLOS, as well as matters specifically provided for in other international agreements conferring jurisdiction on the Tribunal. Although this article does not explicitly grant advisory jurisdiction, Article 138(1) of the ITLOS Rules provides that if an international agreement related to the purposes of the Convention expressly authorizes ITLOS to give an advisory opinion, the Tribunal may do so on legal questions. Thus, while neither UNCLOS nor the Statute explicitly grants ITLOS such competence, the Rules establish a procedural basis for it. The ITLOS Advisory Opinion on Climate Change and International Law (Case No. 31) issued on 21 May 2024 was based on such a mechanism: nine small island States established the Commission of Small Island States on Climate Change and International Law (COSIS) through a dedicated treaty, which then became the requesting entity. If South China Sea claimant States were to establish a similar body, they could, by analogy, circumvent the principle of State consent and request an advisory opinion from ITLOS.

By Contrast, arbitration under Annex VII of UNCLOS presents the most immediate and pragmatic legal pathway for South China Sea claimant States, particularly in light of the South China Sea Arbitration initiated by the Philippines under Article 287 of UNCLOS. Despite China’s declaration under Article 298 of UNCLOS to exclude sovereignty and delimitation disputes from compulsory settlement of disputes mechanism, the Arbitration demonstrated how claimant States could “repackage” their claims in ways that focus on the interpretation and application of specific UNCLOS provisions, rather than directly challenging China’s territorial sovereignty and maritime interests. Since Annex VII arbitration functions as a “residual” mechanism under UNCLOS, and ratification of the Convention entails automatic acceptance of its jurisdiction, declaratory exclusions made under Article 298 of UNCLOS have proven to be of limited practical protection. As a matter of fact, in recent years, Philippine officials have publicly expressed intentions to initiate a “second arbitration” against China concerning the South China Sea. Therefore, among the three legal pathways, Annex VII arbitration remains the most likely avenue for future actions by the claimant States.

II. Potential Issues for Further Lawfare in the South China Sea

Should the Philippines and other claimant States pursue legal action against China, they are likely to focus on several key issues that challenge China’s claims in the South China Sea.

One of the most prominent issues is China’s non-compliance with the 2016 South China Sea Arbitration Award, which invalidated much of China’s claims in the South China Sea. Although China has consistently rejected the ruling, the Philippines and other claimant States could use this as a basis to mobilize international support for further legal challenges. If the Philippines were to seek an advisory opinion on China’s failure to comply with the Award, it might potentially garner political and legal backing within the UN General Assembly or other international forums, thereby further isolating China diplomatically.

Environmental protection issues are also likely to feature in future legal claims. With the growing global emphasis on marine conservation and sustainable use of ocean resources, claimant States may seek to challenge China’s actions in the South China Sea on environmental grounds. This could include accusations of damage to marine ecosystems or the over-exploitation of marine resources, as a 2023 report published by the Washington-based Center for International and Strategic Studies (CSIS) illustrates. Furthermore, disputes related to the newly established Huangyan Dao Nature Reserve and the broader management of marine biodiversity might also become key points of contention in future legal battles.

Another area of potential legal action is the interpretation of specific UNCLOS provisions. Claimant States may seek to challenge China’s published straight baselines around Scarborough Shoal (Huangyan Dao) and Paracel Islands (Xisha Qundao), questioning whether these baselines conform to the requirements set out in UNCLOS. Additionally, the issue of “historic rights” and whether these rights are compatible with UNCLOS may continue to be a central legal battleground, with the Philippines and others seeking to press China to clarify its legal implications.

III. China’s Strategic Responses: “Embracing” Lawfare in the South China Sea

As the Philippines and other claimant States increasingly employ legal means to press their claims, it is vital for China to adopt a positive strategic approach to managing this growing “lawfare” in the South China Sea by “embracing” it. While legal challenges are an inevitable aspect of international relations, they also present an opportunity for China to reshape the narrative around its long-time claimed maritime rights and territorial sovereignty.

First and foremost, the priority for China is to continue to engage diplomatically with other claimant States, particularly within regional forums like ASEAN, to emphasize its commitment to maintaining peace and stability in the South China Sea. Diplomatic efforts are traditionally known for their effectiveness for preventing further escalation and reaffirming that the South China Sea is a core national interest for China. By fostering closer relationships with ASEAN States and promoting possible mutually beneficial agreements, China could reduce the likelihood of a “united front” among claimant States and external actors seeking to challenge its position.

Secondly, from a legal perspective, China will need to continue defending its sovereignty in international legal forums. While China’s non-consent to the jurisdiction of the ICJ and the ITLOS offers a degree of protection, its participation in broader legal discussions (such as the annual Meetings of Parties to the UNCLOS and general discussion at the UNGA) remains necessary to uphold the principles of international law.

In parallel, China’s approach to environmental issues in the South China Sea should be both proactive and strategic. As global attention on environmental protection grows, it will be important for China to position itself as a leader in sustainable maritime management by advancing initiatives such as the Huangyan Dao Nature Reserve and other regional environmental protection cooperations. By demonstrating its commitment to ecological sustainability, China can deflect criticisms that frame its actions in the South China Sea as environmentally damaging or irresponsible.

Finally, it is essential for China to continue to enhance its domestic legal infrastructure to better respond to international legal challenges. This includes building a robust team of legal experts specializing in international law of the sea, developing contingency plans for various legal scenarios, and ensuring that China’s legal arguments are presented consistently and effectively in international forums. Additionally, China could also invest in public diplomacy efforts to communicate its legal positions clearly and persuasively, both to domestic and international audiences, in order to shape global perceptions of its actions in the South China Sea.

Conclusion

The Philippines’ legal offensive in the South China Sea represents a key element of the evolving lawfare in the region, as claimant States increasingly turn to international legal mechanisms to challenge China’s maritime claims. As this trend continues, China shall develop comprehensive diplomatic, legal, and strategic responses to safeguard its territorial interests and uphold its sovereignty. By anticipating the legal pathways that may be pursued by claimant States and positioning itself as a responsible, proactive actor in the region, China can navigate the complexities of lawfare in the South China Sea while maintaining stability and fostering long-term regional cooperation.

(Dr. Yinan Bao is an associate research fellow at Huayang Center for Maritime Cooperation and Ocean Governance, and non-resident fellow at ICAS. The thoughts and opinions expressed are those of the author and not necessarily those of the Huayang Center for Maritime Cooperation and Ocean Governance or ICAS.)