Author: Krishna Soni
College: SAGE University, Bhopal
LinkedIn Profile: https://www.linkedin.com/in/krishna-soni-03166b279/
In Brief
International water boundaries spark tension among countries more than most global rules do. The international water always meant more than water – it means oil, fish, trade routes,and strategic military positioning. When one nation claim it owns part of the ocean and another says no, that area belongs to us instead. Talks get stuck easily when lines on maps collide. Disagreements stretch into years, court cases pile up, occasionally ships face each other near contested zones.
Back in 1982, nations agreed on a new rulebook for oceans – UNCLOS. It started working in 1994, meant to bring order where none existed before. Over 160 countries said yes by signing on, showing rare global unity. Instead of chaos, lines would now mark boundaries at sea. Rights near shores belong to coastal governments; farther out belongs to everyone. Disagreements? There are ways to sort them without firing shots. Yet just because something is signed doesn’t mean it’s followed. Nowhere shows that better than the waters off Southeast Asia. One strong nation ignored a court ruling there – and nothing much changed after. Rules matter less when power refuses to bend.
The nine-dash line drawn by China runs through waters claimed by Vietnam, the Philippines, Malaysia, and Brunei. Back in 2016, a court formed under UNCLOS rules tore apart the legal reasoning behind that boundary. Beijing reacted by calling the decision meaningless. What emerges is a gap – law on one side, power on the other – and it shapes everything discussed here. Elsewhere, Japan faces off with China near disputed islands in the north. Up in the Arctic, thawing ice reveals fresh competition over land and energy. Tools exist within global law to tackle such fights. Past rulings helped build those tools. Yet how much they can truly fix remains uncertain.
Key Legal Terminology
Understanding maritime disputes requires getting to grips with some specific legal concepts. These are not just technical terms — each one determines how much sea a country can claim, what it can do there, and on what legal basis.
Territorial Sea: Under Article 3 of UNCLOS,12 nautical miles out from shore, a coastal state controls the water completely under international law. Ships from other nations can move through, yet local rules still apply. Arguments usually flare up far past these waters.
Exclusive Economic Zone (EEZ): Out past the coast, stretching 200 nautical miles, lies a stretch governed by UNCLOS Part V. Here, a country holds first claim on fishing, oil drilling, along with mineral extraction. Ownership of water? Not quite – others sail or fly through without needing permission. Yet what comes from the seabed or waters stays under national control by law.
Continental Shelf: Out past the 200-nautical-mile mark, a country can still hold authority under Article 76 – so long as the seafloor keeps stretching like it began. When landmass pushes farther, claims might stretch beyond 350 miles. Such cases wind up reviewed by the CLCS, where boundaries face scrutiny based on how Earth built them.
Baseline: The starting line from every sea zone begins its count. Usually, it traces the edge where water dips lowest beside land. Bays or rivers might get connected by straight lines instead – Article 7 allows that. Some say China goes too far with its claimed edges near the Paracel Islands.
Freedom of Navigation: Protected by Article 87, every nation holds the freedom to move ships across international waters untouched. Through FONOPs, the U.S. sails often in the South China Sea, testing limits it views as unlawful barriers to that access.
Historic Title: Out of past practice at sea grows a kind of claim, one that stands apart from today’s legal rules. This idea feeds into China’s nine-dash line, drawn across maps with old usage as reason. Judges in the 2016 ruling found it did not fit within modern treaty law.
Delimitation:One state might share sea borders with another,a boundary must be drawn. Starting from equal distance between shores happens first, though fairness can shift things later. Judges looked at the North Sea dispute back in 1969, which set how it’s usually done now.
Dispute Settlement under UNCLOS: Part XV of UNCLOS gives states access to compulsory third-party adjudication. They can go to the International Tribunal for the Law of the Sea (ITLOS), the International Court of Justice (ICJ), or an Annex VII arbitral panel. The key word is compulsory — a state cannot block another from initiating proceedings simply by refusing to participate.
Low-Tide Elevation: Water covers it when the tide rises, though it stays exposed when levels drop. Not considered an island under UNCLOS Article 13, so lacks any claim to surrounding waters. That detail shaped key findings in the 2016 ruling about the South China Sea.
Archipelagic Baselines: Straight lines linking farthest islands are allowed under Article 46 for nations made up entirely of island groups. Such countries include the Philippines and Indonesia. Sovereignty reaches much farther across waters because of these connected points. Sea control grows in scope when those boundaries are drawn.
The Evidence
Maritime disputes are not fought only on water. They are also fought through documents, maps, and legal filings. The evidentiary record in cases like the South China Sea arbitration runs to thousands of pages. Here are the main categories of evidence that courts and tribunals have relied on:
Treaty Texts and Ratification Records: What countries agreed to – and when – shapes how ocean rules are interpreted today. The UNCLOS treaty sits alongside older deals, such as the 1898 Treaty of Paris and the postwar 1951 San Francisco Peace Treaty, as key records. Disputes about maritime law often hinge on these documents. Timing and signatures carry heavy weight in those debates. Paper trails decide jurisdiction.
Arbitral Awards and Court Judgments: Back then, choices made still matter now. Take the 2016 ruling on the South China Sea – it stuck. So did the North Sea shelf case from 1969. Then came Nicaragua versus Colombia in 2012. After that, the Bay of Bengal decision in 2014. Each set a pattern others followed.
Historical Maps and Cartographic Records: Maps are tricky evidence. States often produce centuries-old charts to support their claims. But the 2016 tribunal found that no Chinese map actually showed the nine-dash line as a boundary — it appeared as a vague line without legal definition. Cartographic evidence can equally undermine a claim as support it.
State Practice and Diplomatic Notes: How states actually behave in disputed waters — whether they patrol, license oil exploration, arrest foreign fishermen, or file diplomatic protests — feeds directly into the legal analysis. A state that tolerates another’s conduct for decades may find that silence counts against it.
CLCS Submissions and Scientific Data: For extended continental shelf claims beyond 200 nautical miles, states must submit detailed scientific and hydrographic data to the CLCS. These submissions, and the counter-submissions they generate from neighbouring states, form a growing body of evidence in overlapping continental shelf disputes.
Freedom of Navigation Operations: The US Navy’s FONOPs are themselves a form of state practice. By deliberately sailing through areas where coastal states assert excessive restrictions, the United States creates a record challenging those claims under customary international law — a strategic use of naval operations as legal argument.
Synopsis
Every year, ships carry about 3.4 trillion dollars in goods across the South China Sea. This stretch of water sees more shipping traffic than any other conflict zone on Earth. IT holds significant amounts of oil and natural gas,and the fisheries it supportsfeed million across Southeast Asia. That combination of money, energy, food, and location collide, explain why this region is highly sensitive.
China’s assertion via the nine-dash line didn’t align with maritime zones under UNCLOS. Instead of clarity, Beijing offered shifting explanations – sometimes calling it historic waters, sometimes focusing on islands inside the boundary, at other times referring vaguely to “relevant rights.” This lack of precision seems chosen, not accidental. When the 2016 arbitration panel reviewed the matter, it dismissed such uncertainty outright. Upon joining UNCLOS, they ruled, a country gives up older claims that clash with its terms. Out of nowhere, the Philippines filed a claim while China stayed away completely. Even so, the court moved forward – allowed by rules tucked inside UNCLOS Annex VII. Its authority wasn’t up for debate.
Not long ago, a decision brought clarity through two clear outcomes. Starting with reefs like Mischief, McKennan, and Subi – these sit above water only at low tide, so they count as tiny bumps, not real islands. Because of that fact, no sea rights come from them, even after heavy building work. On another note, when China blocked Philippine boats from fishing or looking for energy underground inside their own waters, it crossed a legal line recognized by global rules. A scrap of paper – that is what China labeled the ruling. Under Duterte’s leadership, Manila chose quiet over confrontation, trading principle for profit with Beijing. Legally, it matters. Diplomatically, it fades into background noise.
Over there, tensions linger in the East China Sea around the Senkaku/Diaoyu Islands, caught between Japan and China, with no official ruling in sight since Tokyo prefers avoiding courts where results can’t be guaranteed. Suddenly, melting ice reshapes the Arctic, uncovering sea paths and buried riches once locked beneath frozen depths. Russia tosses in its claim, then Canada follows, Denmark joins too, and Norway adds another filing – all handed to the CLCS for review. Slowly, paperwork moves forward within established rules, giving the polar region a steadier path compared to chaos further south – at this moment anyway.
Landmark Case Laws
1. The Republic of the Philippines v. The People’s Republic of China (PCA Case No. 2013-19, 2016)
This is arguably the most consequential maritime law decision of the past thirty years. The tribunal dismantled the nine-dash line by holding that UNCLOS does not permit historic rights claims that exceed what the Convention itself grants. It also ruled on the status of individual features — Scarborough Shoal, for instance, is a rock under Article 121(3), entitling it only to a 12-nautical-mile territorial sea, not an EEZ. The case demonstrated that Annex VII arbitration can proceed even when a major state refuses to participate. It has since become the standard legal reference point in South China Sea diplomacy.
2. North Sea Continental Shelf Cases (ICJ, 1969)
Caught between Denmark and the Netherlands, Germany stood to gain far less seabed under strict equidistance lines. Not bound by rigid formulas, the ICJ ruled instead for fair outcomes in dividing underwater zones. From this emerged the view: a nation’s seabed rights grow out of its mainland, not gifts from treaties. Ever since, courts quoting this stance have shaped decisions on claims beneath polar oceans too.
3. Bay of Bengal Maritime Boundary Arbitration: Bangladesh v. India (PCA, 2014)
Bangladesh’s concave coastline, under a strict equidistance calculation, would have produced a boundary that cut off its access to a large portion of the Bay of Bengal. The tribunal adjusted the line to correct this distortion, giving Bangladesh a significantly larger maritime area. One interesting feature of the case was the disputed low-tide elevation of South Talpatty/New Moore Island, which had by the time of the proceedings already submerged due to sea level rise. This raised a question the tribunal did not need to fully resolve but which is becoming increasingly pressing: what happens to maritime boundaries when the geographic features they depend on disappear?
Final Remarks
International maritime law has come a long way since states simply drew lines on maps and dared each other to cross them. UNCLOS created a genuine legal framework — one with defined zones, binding dispute resolution, and an institutional infrastructure to support it. The fact that over 168 countries have ratified it says something about its legitimacy.
But the South China Sea experience is sobering. When a permanent member of the UN Security Council dismisses an arbitral award as illegitimate and faces no meaningful international consequence, the limits of the legal system become visible. UNCLOS has no enforcement arm. The ICJ cannot compel compliance. ITLOS can issue provisional measures, but states can ignore them. What keeps international law functioning is ultimately a mix of reciprocity, reputational cost, and the practical benefits of a predictable legal order. That calculus breaks down when geopolitical stakes are high enough.
The coming decades will test maritime law in new ways. Sea level rise is not a hypothetical — Pacific island nations are already raising the question of whether they will retain their EEZs if their land territory becomes uninhabitable or submerges entirely. The Arctic is opening up, and the CLCS is processing competing extended shelf claims that overlap in legally complex ways. Deep seabed mining under the International Seabed Authority regime is moving from theory to practice, bringing new resource conflicts.
None of these problems is beyond the capacity of international law to address, provided states are willing to engage with the legal process in good faith. The tools — UNCLOS, the ICJ, ITLOS, Annex VII arbitration, the CLCS — exist. What the South China Sea dispute has shown is that legal tools are only as strong as the political commitment behind them.
Frequently Asked Questions
What exactly is UNCLOS and why does it matter?
UNCLOS is the main international treaty governing how states use and divide the world’s oceans. It sets out the boundaries of maritime zones — territorial sea, EEZ, continental shelf — and specifies what rights states have in each. It also provides compulsory dispute settlement procedures. Without it, maritime boundary disputes would be resolved almost entirely by power rather than law.
Is China’s nine-dash line legal under international law?
No — at least not as an UNCLOS-compatible claim. The 2016 South China Sea arbitral tribunal held that UNCLOS, once ratified, extinguishes any prior historic rights inconsistent with it. China’s nine-dash line, to the extent it claims resource rights beyond what UNCLOS permits, has no legal basis. China disputes this interpretation and has not withdrawn the line.
Can an artificial island create maritime zones for a state?
No. Under UNCLOS, only naturally formed islands can generate maritime zones. Article 60(8) explicitly states that artificial islands do not have the status of islands under UNCLOS and generate no territorial sea, EEZ, or continental shelf of their own. The 2016 tribunal confirmed that even naturally formed but very small features — if they cannot sustain human habitation on their own — generate only a 12-nautical-mile territorial sea at most.
How are disputed maritime boundaries actually drawn?
Courts and tribunals generally start with a provisional equidistance line — the line equidistant from both states’ coasts. They then adjust it to account for relevant circumstances, such as the presence of small islands near the opposing coast or a significantly concave coastline that produces a distorted result. Finally, they check whether the resulting boundary is proportionate to the length of each state’s relevant coastline. This three-stage approach was refined in Nicaragua v. Colombia (2012) and is now standard practice.
What happens if a state refuses to comply with an international maritime ruling?
This is the uncomfortable reality of international law — there is no global police force. States that lose cases before the ICJ or ITLOS can face diplomatic pressure, reputational costs, and trade consequences, but there is no direct enforcement mechanism. Under Article 94 of the UN Charter, a prevailing party can take a non-compliant state to the Security Council, but a permanent member can simply veto any enforcement resolution. The practical tools are political rather than legal, which is why judicial outcomes alone rarely resolve the disputes they adjudicate.
