The South China Sea functions as a disputed maritime area where international legal systems interact with the political strength and defence mechanisms of the region.
The Permanent Court of Arbitration at The Hague delivered a historic decision in 2016 through the United Nations Convention on the Law of the Sea (UNCLOS), which invalidated China’s nine-dash line territorial claim. The ruling from 2023 became irrelevant when Beijing started intensifying its coercive measures in 2025 through island construction and blocking supply ships with coast guard and militia boats, and establishing unauthorised maritime zones, including the September 2025 declaration of Scarborough Shoal as a marine reserve.
The legal system for these actions stems from UNCLOS, which outlines maritime rights and creates rules for exclusive economic zones (EEZs) and freedom of navigation. The 2016 arbitral award established a legally binding status under international law, which confirmed that China’s nine-dash line has no legal basis and established that Second Thomas Shoal, along with other features, qualify as low-tide elevations which do not produce territorial seas. The South China Sea dispute remains unresolved because Beijing maintains its claim of historic rights to approximately 62 per cent of the sea territory. Satellite imagery and open-source reports from 2025 show that the Paracels and Spratlys have become more militarised through the construction of fortified outposts and airstrips and missile installations, and radar networks. The Stimson Centre, along with other organisations, tracked the development of subsidised fishing fleets into paramilitary forces, which now use disputed waters to deter other claimants from entering these areas. More than twenty fortified outposts exist in the Paracel Islands and several in the Spratlys, according to reports, which include airstrips and short-range missile sites and integrated radar systems. The installations, together with the Second Thomas Shoal blockages by coast guard and militia ships, prove China’s strategic move to gain control of the area through unofficial means.
The situation creates two major problems because of international law breaches and inadequate performance from regional organisations. Major powers can disregard legal judgments without facing consequences because China continues to ignore UNCLOS and PCA decisions. The trend works against international court legitimacy while making more countries doubt the current international legal systems. The consensus-based method of ASEAN has evolved into a major weakness of the organisation. While the Philippines and Vietnam have protested against Chinese incursions, other member states hesitate to confront Beijing due to substantial economic ties and fears of retaliation. The regional response remains uncoordinated, which allows for step-by-step “salami-slicing” operations that modify the maritime situation.
The operational and strategic challenges are considerable. The Chinese military employs “grey-zone” operations through vessel ramming and water cannon use and close-in blocking tactics, and civilian and paramilitary vessel integration, which stay beneath armed conflict boundaries, thus making deterrence efforts challenging. Many Southeast Asian states lack the maritime domain awareness, coastal surveillance, and modern coast guard fleets needed to deter or respond to these actions. The detection and countermeasures against ongoing harassment require multiple technological improvements because many claimant states need better satellites and radar systems and automatic identification systems, and unmanned surface and aerial systems. The absence of these capabilities enables small incidents to escalate into major problems, which politicians exploit for political advantage which harming public confidence in regional stability and legal systems. The United States faces two major challenges in its foreign policy because its economic ties with China restrict its ability to take strong diplomatic actions and because there are doubts about the long-term stability of U.S. commitments to its allies. The United States and Japan, and the Philippines conduct joint exercises to demonstrate their commitment, but China views these actions as foreign interference, which heightens the chances of unintended conflicts.
The path to progress demands both a moral evaluation process and effective solution development. ASEAN needs to stop its cautious approach by creating a joint declaration that opposes forced actions in the South China Sea while using the 2016 arbitral ruling to establish maritime rights. The initiative strengthens ASEAN’s dedication to international law by showing that the region will not permit any country to modify maritime rights. ASEAN must expedite its talks to establish a legally enforceable Code of Conduct with China, which should contain both enforcement mechanisms and dispute resolution processes rather than maintaining it as an unenforceable document. ASEAN requires external partners to support its normative position through specific strategic measures. The United States and its allies should maintain freedom of navigation operations while they enhance coordinated patrols and exercises and develop partner capacity through platform and sensor provision and training for coast guards and navies. The success of Allied policy depends on continuous joint work because credibility needs both long-term presence and reliable commitments and initiatives, which enable regional states to protect their maritime rights without creating unnecessary conflicts. Allies need to focus on non-kinetic tools, which include legal help for international case preparation and public diplomatic efforts to maintain a worldwide focus and targeted sanctions against coercion facilitators and investments in logistics systems that make it harder for a nearby power to operate effectively. The combination of tangible capability transfers with robust diplomatic initiatives will make coercion less sustainable while increasing its long-term costs.
International law faces a critical test in 2025 because of the South China Sea events, which demonstrate how major powers can disregard legal frameworks. China continues to militarise its territory and weaponise its fishing fleets and establish the Scarborough reserve without international approval, which violates UNCLOS and the 2016 PCA ruling.
ASEAN’s lack of action and internal division has enabled the steady breakdown of legal standards, yet this problem remains solvable. ASEAN requires two elements for success: it must establish both normative leadership and binding maritime governance systems, while the United States and its allies must maintain their strategic military presence to stop future territorial breaches. The South China Sea needs established legal boundaries together with defensive military strength to maintain its status as an international sea under legal governance instead of military control.
