Delimitation of Maritime Boundaries

In one line

Where two States' maritime zones overlap, the boundary is drawn by agreement in order to achieve an equitable solution, and equidistance is a starting point rather than a rule.

In the wording a student can write in an exam: the delimitation of the territorial sea between States with opposite or adjacent coasts is governed by article 15 of the Convention on the Law of the Sea, which applies the median line unless historic title or other special circumstances require otherwise. The delimitation of the exclusive economic zone and of the continental shelf is governed by articles 74 and 83, which require delimitation by agreement on the basis of international law in order to achieve an equitable solution. Courts and tribunals now apply a three-stage method: a provisional equidistance line, adjustment for relevant circumstances, and a check against disproportion.

Three provisions, two standards

Article 15, the territorial sea. Where the coasts of two States are opposite or adjacent, neither is entitled, failing agreement between them to the contrary, to extend its territorial sea beyond the median line every point of which is equidistant from the nearest points on the baselines from which the breadth of each State's territorial sea is measured. That does not apply where it is necessary by reason of historic title or other special circumstances to delimit the territorial seas in a way which is at variance with it.

Articles 74(1) and 83(1), the exclusive economic zone and the continental shelf. Delimitation shall be effected by agreement on the basis of international law, as referred to in article 38 of the Statute of the International Court of Justice, in order to achieve an equitable solution. Both articles add that if no agreement can be reached within a reasonable period the States concerned shall resort to the procedures in Part XV, and that pending agreement they shall make every effort to enter into provisional arrangements of a practical nature.

Notice the difference. Article 15 states a rule, the median line, with an exception. Articles 74 and 83 state no rule at all: they state an objective, an equitable solution, and leave the method open. That drafting was deliberate, because UNCLOS III could not agree between the equidistance camp and the equitable-principles camp, and the two cases below are why.

The first case: equidistance rejected

Facts. North Sea Continental Shelf Cases (Federal Republic of Germany/Denmark; Federal Republic of Germany/Netherlands), ICJ Reports 1969, page 3, judgment of 20 February 1969. Germany, Denmark and the Netherlands had agreed partial continental shelf boundaries near the coast in 1964 and 1965 but could not agree on their prolongation. Denmark and the Netherlands wanted equidistance, as in article 6 of the 1958 Geneva Convention. Germany's North Sea coast is concave, and equidistance lines drawn from a recessing coast meet a short way out and cut off the State behind them from the shelf beyond; the convex coasts of Denmark and the Netherlands had the opposite, widening effect. Germany had signed but never ratified the 1958 Convention. By two special agreements of 20 February 1967 the parties asked the Court to state the applicable principles.