Internationaal recht – North Sea Continental Shelf Cases

Case

The Netherlands, Denmark and Germany disagreed about how the continental shelf of the North Sea should be defined. The Netherlands and Denmark were both parties to the 1958 Geneva Continental Shelf Convention. In that treaty a specific provision was included, Article 6, which regulated the demarcation of a continental shelf. This article stipulated, among other things, that the continental shelf could be demarcated by means of the so-called ‘equidistance rule’ or a line consisting of points that lie just as far from the coast of one state to the coast of the other state. However, Germany was not a party to this Treaty. As a result thereof, the Netherlands and Denmark could not rely on Article 6 of this Convention. For this reason, the Netherlands and Denmark argued that Article 6 had developed into a rule of customary international law. This would mean that Germany would also be bound by the ‘equidistance rule’ (paragraph 70).

Legal question

Has Article 6 of the 1958 Geneva Continental Shelf Convention developed into a rule of customary international law?

International Court of Justice

According to the Court, a rule from a treaty, such as Article 6 of the Geneva Continental Shelf Convention, can indeed form the basis for the development of a rule of customary international law, as the Netherlands and Denmark argued. However, such a treaty rule must have a certain character. The behaviors in question must result in a fixed practice, and they must be performed or complied with in a way that shows that there is also a conviction that action must be taken in this way. Therefore, the use of the equidistance rule had not developed into a rule of customary international law.