Maritime Boundary Disputes Between Bangladesh and Myanmar

When most people think about disputes between neighbouring countries, they picture soldiers facing off across a fenced land border. The relationship between Bangladesh and Myanmar tells a different story. The two share a land boundary of roughly 270 kilometres that has stayed largely settled, yet for decades they argued bitterly over something far harder to draw a line through: the open waters of the Bay of Bengal. Beneath those waters lie oil and gas reserves valuable enough to make a stretch of sea worth taking to an international court. This post explains what the dispute was about, how it was eventually settled, and why tensions between the two countries have not fully disappeared.

Why the sea, not the land, became the problem
The role of the Bay of Bengal’s resources
The legal framework: UNCLOS and ITLOS
How the Tribunal actually drew the line
Bangladesh’s concave coast problem
The puzzle of St. Martin’s Island
The “grey area” beyond 200 nautical miles
Who won?
The Rohingya crisis: a wound the court could not heal
How the crisis reshaped bilateral relations
What this dispute teaches us

Why the sea, not the land, became the problem

The land border between Bangladesh and Myanmar runs along the Naf River and through hilly terrain in the southeast. While this border has its own security headaches, the two governments never seriously contested where the line should sit. The sea was a completely different matter.

The trouble is that maritime boundaries are not just about where a country’s beach ends. Under international law, a coastal state can claim several overlapping zones stretching out into the ocean. These include a territorial sea of up to 12 nautical miles, an exclusive economic zone (EEZ) of up to 200 nautical miles where the state controls fishing and resource extraction, and a continental shelf that can sometimes extend even further. When two countries sit close together along a curved coastline, these zones collide. Someone has to decide who gets what.

Tensions came to a head in October 2008, when survey ships working under a licence from Myanmar began operating near St. Martin’s Island, in waters Bangladesh considered its own. With energy companies eager to explore the seabed, the disagreement was no longer theoretical. Both sides wanted certainty before drilling could begin.

The role of the Bay of Bengal’s resources

The Bay of Bengal is rich in hydrocarbons, and advances in deep-water technology made reserves that were once unreachable suddenly worth fighting over. For both Bangladesh and Myanmar, securing rights to these gas blocks meant securing future energy supplies and revenue. This is the practical core of the dispute: the maps mattered because the seabed beneath them held money and energy security.

The legal framework: UNCLOS and ITLOS

Both countries are parties to the United Nations Convention on the Law of the Sea (UNCLOS), the 1982 treaty that functions as the constitution for the world’s oceans. UNCLOS sets out how maritime zones are measured and how boundaries between neighbouring states should be drawn. It also created the International Tribunal for the Law of the Sea (ITLOS), an independent court based in Hamburg, Germany, to settle exactly these kinds of disagreements.

After years of failed negotiations, both governments agreed to let ITLOS decide. In late 2009 they formally consented to the Tribunal’s jurisdiction, and Bangladesh invited the court to resolve the maritime boundary dispute. This was a notable step. Rather than letting the quarrel fester or escalate, two neighbours chose to hand the decision to neutral judges and accept the outcome.

The case carried historic weight. It was the first time ITLOS had ever ruled on a maritime boundary, and the first time an international court determined the seabed boundary of both the exclusive economic zone and the extended continental shelf. The judgment was delivered on 14 March 2012.

How the Tribunal actually drew the line

To understand the verdict, it helps to know the method ITLOS used. The Tribunal followed a three-step approach that international courts have refined over decades. First, it draws a provisional equidistance line, which is simply a line where every point is an equal distance from the nearest coast of each country. Second, it checks whether any relevant circumstances make that line unfair and adjusts it if needed. Third, it tests the result for proportionality, making sure the share of sea each country receives is not wildly out of line with the length of its coast.

Bangladesh’s concave coast problem

Bangladesh had a genuine grievance with the plain equidistance method. Its coastline is sharply curved inward, a shape lawyers call concave. When you draw equidistance lines from a concave coast squeezed between two neighbours, the lines bend toward each other and “cut off” the middle country, choking its access to the open sea. Bangladesh argued this was unjust and asked the Tribunal to use a different technique called the angle-bisector method instead.

ITLOS stuck with equidistance as the starting point but agreed that Bangladesh’s concave coast was a relevant circumstance. The Tribunal accepted that the concave coastline produced a cut-off effect that required adjusting the provisional line to reach an equitable result. In effect, the judges acknowledged the geography was working against Bangladesh and shifted the boundary to compensate.

The puzzle of St. Martin’s Island

One of the most debated parts of the case involved St. Martin’s Island, a small but inhabited Bangladeshi island that sits awkwardly close to the Myanmar coast. The question was how much weight this island should carry when drawing the boundary.

The Tribunal split the difference in an interesting way. For the territorial sea, it treated St. Martin’s Island as a full feature and granted it a 12-nautical-mile territorial sea. But for the much larger EEZ and continental shelf, ITLOS decided not to use the island as a base point, because doing so would have cut off the projection of Myanmar’s coast. The island counted for close-in waters but was set aside for the deeper zones. This reasoning was controversial enough that some judges wrote separate opinions arguing it was not explained clearly enough.

The “grey area” beyond 200 nautical miles

The ruling also broke new ground on the continental shelf beyond 200 nautical miles. ITLOS confirmed that Bangladesh had rights to this extended shelf, but the way the boundary lines fell created an unusual zone known as the grey area. Here, Bangladesh holds rights to the seabed below while Myanmar holds rights to the water column above. It is one of the more creative outcomes in maritime law, requiring the two states to coexist in the same patch of ocean at different depths.

Who won?

Bangladesh treated the judgment as a major victory, and the numbers explain why. The verdict awarded Bangladesh around 111,000 square kilometres of maritime territory, roughly 80 percent of what it had claimed. Just as importantly, the decision unlocked access to offshore gas blocks that had been frozen by the dispute.

It is more accurate, though, to call the outcome a balanced settlement than a knockout win. The Tribunal adjusted the boundary in Bangladesh’s favour to fix the cut-off problem, but it also rejected several of Bangladesh’s bolder arguments, including its push to use the angle-bisector method and its claim that the geology of the Bengal seabed entitled it to more shelf. Both countries accepted the binding ruling, and the case became a textbook example of two neighbours resolving a resource conflict peacefully rather than through force.

The settlement had a ripple effect, too. When Bangladesh later took a similar maritime dispute with India to arbitration, it dropped its geological argument after the ITLOS ruling had already rejected that line of reasoning. One verdict helped shape the next.

The Rohingya crisis: a wound the court could not heal

Settling the sea did not settle the relationship. The single largest strain on Bangladesh-Myanmar ties has nothing to do with boundaries and everything to do with people. The Rohingya, a Muslim minority from Myanmar’s Rakhine State, have fled across the border in waves for decades, but the largest exodus came in 2017.

Following a military crackdown in Rakhine State, more than 1.3 million Rohingya refugees ended up in Bangladesh, with Myanmar refusing to take them back. Most now live in vast, overcrowded camps around Cox’s Bazar. Bangladesh, which does not formally recognise them as refugees and instead calls them “forcibly displaced Myanmar nationals,” carries an enormous humanitarian and economic burden while repatriation talks repeatedly stall.

How the crisis reshaped bilateral relations

Before 2017, relations were generally workable despite occasional friction. The refugee influx changed that. Researchers note that while trade between the two countries has continued, the crisis has produced security tensions tied to border concerns, trafficking, and militant activity. The 271-kilometre frontier along the Naf River has become a corridor for arms smuggling, drug trafficking, and cross-border crime, turning a once-quiet border into a security worry.

The situation grew more tangled after Myanmar slid into civil war following the 2021 military coup. With armed groups like the Arakan Army contesting control of the very Rakhine State the Rohingya fled, the prospect of a safe, voluntary return has only receded further. The maritime boundary may be fixed on the map, but the human and security dimensions of the relationship remain unresolved.

What this dispute teaches us

The Bangladesh-Myanmar story is really two stories running side by side. One shows international law working as intended: two states with a resource conflict chose a neutral tribunal, accepted a binding verdict, and avoided escalation. Analysts have even pointed to it as a possible model for thornier disputes elsewhere, such as in the South China Sea. The other story is a reminder that courts can divide oceans but cannot resolve everything. Refugees, civil war, and cross-border crime sit outside the reach of any maritime judgment.

For students of South Asian politics, the lesson is that “territorial disputes” rarely fit into neat boxes. A boundary on a chart can be settled cleanly while the deeper relationship between two neighbours stays fragile.

What do you think? Does the peaceful settlement of the maritime boundary suggest that international tribunals are an effective tool for resolving resource conflicts, or does the unresolved Rohingya crisis show the real limits of what such legal mechanisms can achieve? And should economic cooperation in the Bay of Bengal be pursued even while the refugee question remains open?

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Table of Contents

Why the sea, not the land, became the problem 🔗

The role of the Bay of Bengal’s resources 🔗

The legal framework: UNCLOS and ITLOS 🔗

How the Tribunal actually drew the line 🔗

Bangladesh’s concave coast problem 🔗

The puzzle of St. Martin’s Island 🔗

The “grey area” beyond 200 nautical miles 🔗

Who won? 🔗

The Rohingya crisis: a wound the court could not heal 🔗

How the crisis reshaped bilateral relations 🔗

What this dispute teaches us 🔗