The North Sea Continental Shelf Cases

July 7, 2023
IMA Research Team

By Alex Marsh

Six states (the United Kingdom, France, Norway, Germany, the Netherlands, and Belgium) maintain continental shelf claims in the North Sea, a resource-rich and economically important body of water off the coast of western and northern Europe. Control of the continental shelf allows a State the exclusive rights to resource extraction from the seafloor, which is important in hydrocarbon rich regions such as the North Sea.

Figure 1. Established North Sea maritime boundaries.

Since the creation of the concept of a maritime boundary to divide marine natural resources, from fish to oil, delimitation disputes have been relatively common. Each country is incentivized to maximize their total claimed area in an effort to reap the most economic benefit. The North Sea Continental Shelf Cases (Denmark v. Germany & the Netherlands v. Germany) provide an interesting look at how supranational bodies like the International Court of Justice (ICJ) balance precedent, equity, and treaty obligations when resolving inter-state disputes apportioning maritime boundaries.

What was the dispute?

Germany’s continental shelf claims in the North Sea overlapped with those of the Netherlands and Denmark, since Germany measured their coastal baseline in a different manner than other states. The Netherlands and Denmark, located to the west and north of Germany, respectively, have convex coastlines, meaning their coastlines bulge outwards. Germany, on the other hand, has a concave North Sea coastline, meaning it dips inward. If the standard principle of equidistance was used to delimit the state’s continental shelf claims, Germany would end up being “squeezed in” and as a result be left with a smaller area of continental shelf.

Figure 2. Provisional equidistance lines in the North Sea.

With Germany’s preferred delimitation methodology differing so much from those of the Netherlands and Denmark, an area of disputed maritime territory arose. The Netherlands and Denmark wished to delimit the boundary according to the “C-D-E” and “A-B-E” lines in the map below, which are based on equidistance. On the contrary, Germany wished to delimit the boundary according to the “C-D-F” and “A-B-F” lines, arguing that a boundary based on equidistance from their concave coastline would deprive Germany of a continental shelf claim proportional to the size of their North Sea coastline.

Figure 3. Claim lines of Denmark, Germany, and the Netherlands.

Also at issue was the fact that, at the time, Germany was not party to the 1958 Convention on the Continental Shelf, while Denmark and the Netherlands were. The 1958 Convention calls for signatories to use the principle of equidistance when delimiting disputed continental shelf boundaries, which Denmark and the Netherlands wished to apply in this case. Denmark and the Netherlands argued that the 1958 Convention on the Continental Shelf, which specifically holds that such disputes should be resolved with the principle of equidistance, should be applied in this case. Having arrived at an impasse, Germany appealed to the ICJ to litigate the dispute. All states involved agreed to delimit their boundary according to the ruling of the Court. As such, they did not ask the Court to delimit the boundary, only to rule on the underlying assertion that Germany was bound by the 1958 Convention on the Continental Shelf.

The Decision

The ICJ first decided that Denmark’s and the Netherland’s originally separate cases against Germany should be joined, since they had a common interest. The Court held that Germany was not bound by the provisions of Article 6 of the 1958 Convention on the Continental Shelf because Germany was not a signatory to the agreement, and the convention was not yet a part of the “corpus” (body) of international law. Thus, Denmark and the Netherlands had no basis to compel Germany to delimit their disputed boundary via equidistance.

The Court stated that in order for a treaty to become a part of the “corpus” (body) of international law, states must have adhered extensively and almost universally to the principle in question. Furthermore, the Court held that the states in question must, in essence, feel that they are undertaking a legal obligation by adhering to the provisions of the treaty even if they haven’t signed it. The Court felt that, at the time of the case, neither the number of signatories to the 1958 convention (39 states) or the amount of time it was in force (11 years) suggested extensive or near universal adoption.

Lastly, the Court urged all the parties involved to mitigate the impact of “an incidental coastal feature” (Germany’s concave coastline) that could lead to an unjust apportionment of the continental shelf if the principle of equidistance is applied. As a result, Germany was granted most of the additional area they desired, which can be seen by comparing Figure 1 (current North Sea boundaries) to Figure 2 (equidistance). The three States were instructed by the Court to establish an equitable boundary, which was not necessarily based on equidistance but rather by a delimitation methodology agreed on by the states involved.


The Court ultimately found that equidistance was not, as claimed, a priori (customary) rule in international law. Rather, it was to be considered one delimitation option of many in the creation of equitable maritime boundaries. The Court also rejected Germany’s argument that apportionment should be done in such a way that the size of the continental shelf claim was proportional to a state’s coastline, as this would deny states the right to claim “the natural prolongation of their continental shelf.”

Instead, the Court proposed that delimitation should be done on the basis of “equitable principles,” taking multiple factors into account to ensure that each state was granted a fair portion of the contested claim. Following the Court’s ruling, Germany signed agreements with both Denmark and the Netherlands resolving their continental shelf dispute on January 28, 1971. Consequently, these agreements required the United Kingdom to adjust the endpoints of its continental shelf boundaries with Denmark and the Netherlands, which created a completely new continental shelf boundary with Germany, as the UK’s existing boundaries were based on the endpoints of the previous equidistance-based boundaries between Denmark and the Netherlands.

In all, the ICJ’s ruling in the North Sea Continental Shelf Cases (Federal Republic of Germany v. Netherlands & Federal Republic of Germany v. Denmark) was, and is, a significant ruling in international law because its findings relate to how conventions and agreements enter the corpus of the international legal framework. Equally significant was the Court’s holding that delimitation by equidistance was not necessarily customary in international law. Equidistance delimitation was, and is, still widely used, but the Court’s emphasis of equity over equidistance set a new precedent for boundary negotiations from 1969 onwards.

If you’re interested in learning more about the maritime boundaries delimited following the Court’s decision in North Sea Continental Shelf Cases check out our reports on the maritime boundaries of Germany–Netherlands and Denmark–Germany.

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