INTRODUCTION
The ‘South China Sea’ region is one of the important ‘resource-rich maritime zone.’ Almost ‘one-third of global shipping’ passes through this region and it contain vast reserves of oil, gas, and fisheries.[1] This region has also been in news due to the disputes arising from sovereignty claims. At the heart of the controversy lies ‘China’s assertion of sovereignty and historic rights’ within the so-called ‘Nine-Dash Line’, an ambiguous line encompassing nearly ‘90 percent of the South China Sea.’
The central problem is whether ‘Nine-Dash Line’, grounded in China’s notion of ‘historic rights’ can coexist with the ‘maritime entitlements’ and ‘jurisdictional zones’ defined under UNCLOS. The question also raises broader issues about the relationship between customary law and treaty law, interpretation of historic rights, and the authority of international adjudicatory bodies.
HISTORICAL BACKGROUND OF NINE- DASH LINE
The origin of ‘Nine Dash Line’ can be traced to 1947 when an official map was released by the ‘Republic of China outlining an ‘Eleven dash boundary’ covering most of the South China Sea.’ However, this was modified to ‘Nine dash line’ by People’s Republic of China in 1949. The map lacks clear coordinates or legal explanation, creating ambiguity about whether it represents a claim to sovereignty over land features, maritime zones, or the waters themselves.
China has repeatedly claimed that the ‘Nine dash line’ reflects ‘historic rights’ to resources and navigation within this region.[2] The concept of ‘historic rights’ as used by China differs from ‘historic waters’ recognized under international law. Traditional historic waters claims are limited in scope, require long-standing and continuous exercise of authority, and must be acquiesced in by other states.[3] However, China’s claim over this region does not fulfil these conditions as there is no authoritative or historical evidence to show China’s exclusive and consistent control over the region and the demarcated boundary also lacks specific coordinates.
This was also upheld by the arbitral tribunal in ‘South China Sea Arbitration, PCA, 2016’ that “China’s claims to historic rights within the ‘nine-dash line’ are contrary to the Convention and without lawful effect.”[4] The Tribunal clarified that any historic rights inconsistent with UNCLOS were extinguished once a state became a party to the Convention. States’ maritime entitlements must now be derived solely from UNCLOS provisions, not vague notions of history.
The continuing ambiguity over whether the ‘Nine-Dash Line’ represents a claim of sovereignty, historic title, or resource rights has deepened regional tensions. This lack of clarity underscores the urgent need for a definitive legal interpretation consistent with UNCLOS to ensure stability and peaceful resolution of disputes in the ‘South China Sea.’
LEGAL FRAMEWORK UNDER UNCLOS
Often referred as the ‘Constitution of the Sea’, the UNCLOS, 1982 provides a comprehensive legal framework for the ‘maritime governance’ and systematically defines the limits and rights associated with various maritime zones. Beyond these areas lie the ‘high seas’ characterized by principles of freedom, equality, and non-sovereignty, as enshrined in Article 89.[5] Collectively, these provisions establish a uniform, distance-based maritime entitlement system, leaving no legal basis for ambiguous or overlapping assertions such as China’s “historic rights” within the ‘Nine-Dash Line’ which extend beyond the limits prescribed by UNCLOS.
Sovereignty vs. Sovereign Rights under UNCLOS
UNCLOS creates a distinction between sovereignty and sovereign rights where former is applicable only to ‘territorial sea extending up to 12 nautical miles from the baseline’. In this region ‘coastal state’ exercises complete independence and has full authority similar to that over its land territory, subject only to the ‘right of innocent passage.’
Beyond this limit, in “Exclusive Economic Zone and Continental Shelf the coastal states enjoy merely sovereign rights which includes limited powers to explore, exploit and manage the resources.”[6] These rights do not amount to full sovereignty and coexist with the freedoms of navigation and overflight enjoyed by all states.
China’s assertion of ‘sovereignty’ within the ‘Nine-Dash Line’ disregards this legal separation. By extending claims of sovereign control far beyond the territorial sea, China effectively seeks authority over areas that UNCLOS designates as EEZs or high seas. This contradicts Article 89 of UNCLOS which prohibits any state from subjecting parts of ‘high seas’ to its sovereignty. Hence, ‘Nine-Dash Line’ blurs the line between ‘sovereignty and sovereign rights’ undermining the ‘uniform maritime order’ established by UNCLOS.[7]
Exclusion of “Historic Rights” under UNCLOS
UNCLOS makes limited reference to historical claims, acknowledging only “historic bays” and “historic titles” under Articles 10(6) and 15, but it does not recognize any general category of “historic rights.” This textual omission is deliberate and significant. While historic bays and titles relate to clearly defined areas historically subject to state sovereignty and accepted by others, the notion of historic rights as advanced by China extends to vague claims over resources and navigation across open seas.
It further allows states “to exclude disputes concerning historic bays or titles from compulsory dispute settlement, but again omits any reference to historic rights.”[8] This indicates the drafters’ intent to replace indeterminate historical assertions with a uniform legal order based on distance from coastal baselines. The ‘South China Sea Arbitral Tribunal’ affirmed this interpretation holding that ‘any pre-existing historic rights’ inconsistent with UNCLOS were extinguished upon its entry into force. Thus, the Convention’s silence on “historic rights” reflects a conscious shift from politically fluid historical claims to a stable and rule-based maritime regime.
CONTEMPORARY DEVELOPMENTS AND ESCALATING TENSIONS IN THE SOUTH CHINA SEA
In February 2025, a Chinese helicopter reportedly made dangerous maneuvers near a Phillippine government aircraft which was patrolling the ‘Scarborough Shoal’. The ‘Scarborough Shoal’ is a disputed area in ‘South China Sea’ region claimed by both ‘China and Phillipphines.’[9] After a diplomatic protest was lodged by the Phillippines stating this maneuver by China as ‘unprofessional and reckless’, the Chinese administration reverted by claiming that the Phillippine aircraft had illegally intruded what it considers its airspace.
The ‘Philippine Coast Guard’ reported that ‘Chinese Coast Guard vessels’, supported by a PLA Navy helicopter, repeatedly harassed Philippine fisheries vessels conducting a ‘scientific survey’ near Sandy Cay. The persistent interference including close-quarter maneuvers and intimidating aerial passes forced the Philippines to cancel the survey mission altogether.
Such coercive tactics not only undermine the freedom of scientific research and lawful civilian activities in the area but also create a broader chilling effect, deterring regional states from exercising their sovereign rights under UNCLOS.
CONCLUSION
The ‘South China Sea dispute’ centered on ‘China’s assertion of historic rights’ within the ‘Nine-Dash Line’ represents a fundamental challenge to the legal order established by UNCLOS. The historical ambiguity of the ‘Nine-Dash Line’ lacking clear coordinates or consistent state practice, contrasts sharply with UNCLOS’s systematic and distance-based regime of maritime entitlements. The tribunal in ‘Philippines v. China’ decisively affirmed that ‘UNCLOS’ supersedes all prior historic claims and that China’s assertions, whether framed as sovereignty, sovereign rights, or historic entitlements have no lawful effect where they exceed the limits prescribed by Convention.
The tribunal’s findings, especially ‘its rejection of China’s historic rights’ and ‘classification of the Spratly features’ as incapable of generating an EEZ, clarified key legal ambiguities and strengthened the normative authority of UNCLOS. Despite China’s non-compliance, the award remains binding under Article 296 and has significantly shaped international legal discourse and state practice.
Recent incidents including helicopter intimidation at ‘Scarborough Shoal’, harassment of Philippine vessels near Sandy Cay, and China’s deeper operational engagement through the ‘2025 China–Indonesia maritime security MoU’ underscore a widening gap between legal norms and geopolitical realities. These developments reveal escalating militarization, coercive law enforcement, and persistent attempts to enforce contested claims through power rather than law. They also highlight the vulnerability of smaller claimant states whose lawful activities under UNCLOS are increasingly disrupted.
Ultimately, the ‘Nine-Dash Line dispute’ illustrates the central tension between the rule of law and great-power assertion. While UNCLOS provides the definitive legal framework for maritime entitlements, its effectiveness depends on collective adherence and robust enforcement through diplomacy, institutions, and consistent state practice. Ensuring ‘long-term stability in the South China Sea’ will require strengthened regional cooperation, reaffirmation of UNCLOS-based governance, and sustained commitment by the international community to uphold lawful maritime order.
Author(s) Name: Pranav Mishra (Faculty of Law, University of Delhi)
References:
[1] BBC News, “South China Sea dispute: Timeline of key events” (2011) ‘https://www.bbc.com/news/world-asia-pacific-13748349’ (accessed 8 Nov, 2025).
[2] Keyuan Zou and Qiang Ye, “The Relationship between UNCLOS and Customary International Law: Some Reflections”, Marine Policy, Vol. 154 (2023), available at: ‘https://doi.org/10.1016/j.marpol.2023.105691](https://doi.org/10.1016/j.marpol.2023.105691’ (accessed 8 Nov, 2025).
[3] Clive R Symmons, “Historic Waters and Historic Rights in the Law of the Sea: A Modern Reappraisal” (2019) ResearchGate,‘https://www.researchgate.net/publication/334789516_Historic_Waters_and_Historic_Rights_in_the_Law_of_the_Sea’ (accessed 8 November 2025).
[4] ‘Philippines v. China, South China Sea Arbitration’, PCA Case No. 2013-19.
[5] UN Convention on Law of Seas, 1982, art. 89
[6] Id, arts. 56 and 57
[7] Supra note 8.
[8] Id, art 298.
[9] Reuters, “US condemns ‘dangerous’ manoeuvres by Chinese navy in South China Sea,” Reuters, 19 February 2025.
