Delineation methods of French maritime spaces

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Updated on 07/03/2023

Where the coasts of two States are opposite one another or adjacent in such a manner that their maritime spaces (territorial sea, EEZ or continental shelf) overlap (maritime spaces of less than 24 nautical miles for the territorial sea or less than 400 nautical miles for the EEZ and the continental shelf), the States should delimit their maritime spaces.

The States can engage in bilateral negotiations or resort to a dispute settlement procedure in order to come to an agreement on delimitation. In this case, they can refer to the International Court of Justice, the International Tribunal for the Law of the Sea or the ad hoc court of arbitration.




Bilateral negotiation is the most common method for maritime boundary setting between States. These negotiations enable the parties to present their positions as to the geographic characteristics of the space to be delimited and the relevant coasts to be taken into account to do so. They put forward the method or methods they deem the most appropriate and then calculate the boundary coordinates.

These negotiations give rise to the signature of a delimitation agreement which takes effect once ratified by all Parties.

If the States do not come to an agreement, they can resort to an arbitration procedure.



The provisions of the UNCLOS are fairly limited as to maritime space delimitation.

For delimitation of territorial sea, it recommends using the median line (equidistance). However, this method does not apply where another method is required due to the existence of historic title or other special circumstances.

The UNCLOS does not recommend a method for delimiting the EEZ and/or the continental shelf. It simply states that delimitation should arise from an agreement under international law, in order for an equitable solution to be found. Several methods can be applied:

  • equidistant line (with possibility of weighting of certain basic elements of the calculation to achieve an equitable solution – partial effects technique)

  • perpendicular line in the general direction of the coast

  • delimitation using parallels or meridians;

  • use of corridors with parallel lines;

  • bisector method between the general coastal directions.


Some geographical elements may not be taken into account in delimitation if it means cutting off the maritime spaces of a country due to the configuration of the coast (concave or convex coasts, presence of islands, disproportionate coast length). Negotiations can combine several methods for calculating delimitation.

The States can also decide to create joint development zones in which they jointly manage one or several resources according to the provisions they set out together. This method is often used when the States are unable to come to an agreement as to a boundary line.