Foreign Policy Watch: India-Sri Lanka

What is International Maritime Boundary Line (IMBL)?


From UPSC perspective, the following things are important :

Prelims level: IMBL, EEZ, UNCLOS

Mains level: Fishermen issue in India-SL ties

The Tamil Nadu police have issued an alert on the possibility of an attack on fishermen crossing the International Maritime Boundary Line (IMBL) for fishing in Sri Lankan waters.

About International Maritime Boundary Line (IMBL)

  • A maritime boundary is a conceptual division of the Earth’s water surface areas using physiographic or geopolitical criteria.
  • As such, it usually bounds areas of exclusive national rights over mineral and biological resources, encompassing maritime features, limits and zones.
  • Generally, a maritime boundary is delineated at a particular distance from a jurisdiction’s coastline.
  • Although in some countries the term maritime boundary represents borders of a maritime nation that are recognized by the United Nations Convention on the Law of the Sea.
  • The terminology does not encompass lake or river boundaries, which are considered within the context of land boundaries.

The delineation of maritime boundaries has strategic, economic, and environmental implications.


Maritime spaces can be divided into the following groups based on their legal status:

  1. Under the sovereignty and authority (exercising power) of a coastal State: internal waters, territorial sea, and archipelagic waters,
  2. With mixed legal regime, which fall under both the jurisdiction of the coastal State and under the international law: contiguous zone, the continental shelf and the exclusive economic zone, and
  3. That can be used by all States (including land-locked ones) on an equal basis: high seas.

Note: While many maritime spaces can be classified as belonging to the same group, this does not imply that they all have the same legal regime. International straits and canals have their own legal status as well.


The zones of maritime boundaries are expressed in concentric limits surrounding coastal and feature baselines.

  1. Inland waters—the zone inside the baseline.
  2. Territorial sea—the zone extending 12 nm. from the baseline
  3. Contiguous zone—the area extending 24 nm. from the baseline
  4. Exclusive Economic Zone—the area extending 200 nm from the baseline except when the space between two countries is less than 400 nm

Back2Basics: India-Sri Lanka Fisherman Issue

  • There have been several alleged incidents of Sri Lankan Navy personnel firing on Indian fishermen fishing in the Palk Strait, where India and Sri Lanka are only separated by 12 nautical miles.
  • The issue started because of Indian fishermen having used mechanized trawlers, which deprived the Sri Lankan fishermen (including Tamils) of their catch and damaged their fishing boats.
  • The Sri Lankan government wants India to ban use of mechanized trawlers in the Palk Strait region, and negotiations on this subject are undergoing.
  • So far, no concrete agreement has been reached since India favours regulating these trawlers instead of banning them altogether.
  • It has been often a sensitive political issue in Tamil Nadu in the past decade.

About Katchatheevu Island

  • Katchatheevu, an uninhibited off-shore island in the Palk Strait, is administered by Sri Lanka.
  • Though the island was jointly managed by India and Sri Lanka allowing the fishermen of both countries to dry their nets there, it was ceded to Sri Lanka in 1974.
  • Since then, Katchatheevu has remained an issue with some political parties in Tamil Nadu demanding that the island be returned to benefit the fishermen of India.


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