Delimitation of Maritime Boundaries

Procedure International Law Preferred

Process of drawing the line between the overlapping maritime zones of neighbouring or opposite States.

Independent referenceNot an official or legal definition
Sources citedSee the sources at the end of this page
Status Under reviewLast updated 11 October 2026
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Definition

In plain language

When two countries' sea areas overlap, they must agree or be told by a court where each zone ends. This process is called maritime delimitation.

Academic definition

UNCLOS Articles 74 and 83 provide that delimitation of the exclusive economic zone and continental shelf shall be effected by agreement on the basis of international law, as referred to in Article 38 of the ICJ Statute, in order to achieve an equitable solution, while Article 15 applies a median line rule to the territorial sea unless historic title or special circumstances require otherwise. International courts and tribunals apply a three-stage method set out in the Black Sea case (Romania v. Ukraine, 2009): drawing a provisional equidistance line, considering relevant circumstances that may adjust it, and testing the result for disproportion. Delimitation concerns overlapping entitlements and is distinct from determining the limits of a State's entitlement itself.

Classification

Term type
Procedure
Category
International Law
Subject field
Law of the Sea
Subfield
Maritime Delimitation
Difficulty level
Expert
Grammatical category
noun phrase

Language variants

Alternative terms
  • maritime delimitation
  • delimitation of maritime zones
Non-preferred terms
  • not_applicable
Abbreviations
  • not_applicable
Acronyms
  • not_applicable
Native terms
  • délimitation maritime (French)
Transliteration
not_applicable
Pronunciation
not_applicable

Context

Legal effect: Binding

Scope

Covers delimitation between States of overlapping maritime zones; the outer limits of a single State's shelf and land boundary delimitation are separate.

Legal context

UNCLOS Articles 15, 74 and 83, and Part XV dispute settlement, including ICJ, ITLOS and Annex VII arbitration; cases include North Sea Continental Shelf (1969), Black Sea (2009), and Bangladesh/Myanmar (ITLOS, 2012).

Diplomatic context

States negotiate bilateral delimitation treaties, often with joint development arrangements pending agreement, and refer disputes to courts when talks fail.

Institutional context

Handled by foreign ministries, the ICJ, ITLOS, Annex VII arbitral tribunals and the UN Division for Ocean Affairs and the Law of the Sea.

Historical context

The 1969 North Sea Continental Shelf cases rejected equidistance as mandatory and began the equitable principles approach, later replaced by the three-stage method.

Why it matters

Delimitation decides who can license oil, gas and fishing in contested waters and it is a frequent source of maritime disputes.

Usage

Register: Legal

Usage note

Use 'delimitation' for the line between States and 'demarcation' for marking on the ground, which is rarely done at sea.

Example

The tribunal drew a provisional equidistance line and adjusted it for the difference in coastal lengths.

Example scenario

Two neighbouring States claim overlapping exclusive economic zones. After failed talks they submit the dispute to a tribunal, which draws a provisional median line, adjusts it for coastline geography and checks that the final division is not disproportionate.

Common misuse

Treating equidistance as a binding rule in all cases; courts adjust it for relevant circumstances.

Not to be confused with

  • Continental shelf outer limits
  • Land boundary delimitation
  • Joint development zone

Sources

  1. United Nations Convention on the Law of the Sea (1982), United Nations, Articles 15, 74 and 83. un.org
  2. Official definition. not_found_in_source
  3. Treaty reference. un.org
  4. Maritime Delimitation in the Black Sea (Romania v. Ukraine), Judgment, I.C.J. Reports 2009. not_found_in_source
  5. not_found_in_source. not_found_in_source

Source type: Treaty. Source reliability: Primary.

This entry is an independent reference definition, not an official or legally binding text. Where an official definition exists, it is linked above and is authoritative. Read our methodology.

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