North Sea Continental Shelf Cases (Summary)

International Court of Justice Contentious Case: The North Sea Continental Shelf Cases (Germany/Denmark; Germany/Netherlands).

Year of Decision: 1969.

Note: This post discusses only  aspects of the case related to treaty and customary international law.

Overview: The jurisprudence of the North Sea Continental Shelf Cases sets out the dual requirement for the formation of customary international law: (1) State practice (the objective element) and (2) opinio juris (the subjective element). In these cases, the Court explained the criteria necessary to establish State practice – widespread and representative participation. It highlighted that the practices of those States whose interests were specially affected by the custom were especially relevant in the formation of customary law. It also held that uniform and consistent practice was necessary to demonstrate opinio juris – opinio juris is the belief that State practice amounts to a legal obligation. The North Sea Continental Self Cases also dispelled the myth that duration of the practice (i.e. the number of years) was an essential factor in forming customary international law. 

The case involved the delimitation of the continental shelf areas in the North Sea between Germany and Denmark and Germany and Netherlands beyond the partial boundaries previously agreed upon by these States. The parties requested the Court to decide the principles and rules of international law that are applicable to the above delimitation because the parties disagreed on the applicable principles or rules of delimitation. Netherlands and Denmark relied on the principle of equidistance (the method of determining the boundaries in such a way that every point in the boundary is equidistant from the nearest points of the baselines from which the breath of the territorial sea of each State is measured). Germany sought to get a decision in favour of the notion that the delimitation of the relevant continental shelf was governed by the principle that each coastal state is entitled to a just and equitable share (hereinafter called just and equitable principle/method). Contrary to Denmark and Netherlands, Germany argued that the principle of equidistance was neither a mandatory rule in delimitation of the continental shelf nor a rule of customary international law that was binding on Germany. The Court was not asked to delimit because the parties had already agreed to delimit the continental shelf as between their countries, by agreement, after the determination of the Court on the applicable principles.

Facts of the Case:

Netherlands and Denmark had drawn partial boundary lines based on the equidistance principle (A-B and C-D). An agreement on further prolongation of the boundary proved difficult because Denmark and Netherlands wanted this prolongation to take place based on the equidistance principle (B-E and D-E) where as Germany was of the view that, together, these two boundaries would produce an inequitable result for her. Germany stated that due to its concave coastline, such a line would result in her loosing out on her share of the continental shelf based on proportionality to the length of its North Sea coastline. The Court had to decide the principles and rules of international law applicable to this delimitation. In doing so, the Court had to decide if the principles espoused by the parties were binding on the parties either through treaty law or customary international law.

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North Sea Continental Shelf Cases (

Questions before the Court (as relevant to this post):

Is Germany under a legal obligation to accept the equidistance-special circumstances principle, contained in Article 6 of the Geneva Convention on the Continental Shelf of 1958, either as a customary international law rule or on the basis of the Geneva Convention?

The Court’s Decision:

The use of the equidistance method had not crystallised into customary law and the method was not obligatory for the delimitation of the areas in the North Sea related to the present proceedings.

Relevant Findings of the Court:

1. Nature of the treaty obligation: Is the 1958 Geneva Convention, and in particular Article 6, binding on Germany?

1. Article 6 of the Geneva Convention  stated that unless the parties had already agreed on a method for delimitation or unless special circumstances exist, the equidistance method would apply. Germany had signed, but not ratified, the Geneva Convention, while Netherlands and Denmark were parties to the Convention. The latter two States argued that while Germany is not a party to the Convention (not having ratified it), she was still bound by Article 6 of the Convention because:

“…(1)  by conduct, by public statements and proclamations, and in other ways, the Republic has unilaterally assumed the obligations of the Convention; or has manifested its acceptance of the conventional regime; or has recognized it as being generally applicable to the delimitation of continental shelf areas…

(2) the Federal Republic had held itself out as so assuming, accepting or recognizing, in such a manner as to cause other States, and in particular Denmark and the Netherlands, to rely on the attitude thus taken up” (the latter is called the principle of estoppel).

2. The Court rejected the first argument. It said that only a ‘very definite very consistent course of conduct on the part of a State would allow the Court to presume that the State had somehow become bound by a treaty (by a means other than in the formal manner: i.e. ratification) when the State was ‘at all times fully able and entitled to…’ accept the treaty commitments in a formal manner. The Court held that Germany had not unilaterally assumed obligations under the Convention. The court also took notice of the fact that even if Germany ratified the treaty, she had the option of entering into a reservation on Article 6, following which that particular article would no longer be applicable to Germany (in other words, even if one were to assume that Germany had intended to become a party to the Convention, it does not presuppose that it would have also undertaken those obligations contained in Article 6).

3. Note: The Vienna Convention on the Law of Treaties of 1969 (VCLT), which came into force in 1980, discusses in more detail treaty obligations of third States (those States who are not parties to the treaty). It clearly stipulates that obligations arise for third States from a provision of a treaty only if (1) the actual parties to the treaty intended the provision to create obligations for third States; and (2) third State expressly accept those obligations in writing (Article 35 of the VCLT). The VCLT was not in force when the Court deliberated on this case. However, as  seen above, the Court’s position is consistent the VCLT. (See the relevant provisions of the Vienna Convention on the Law of Treaties).

4. The Court held that the existence of a situation of estoppel would have allowed Article 6 to become binding on Germany – but held that Germany’s action did not support an argument for estoppel. The Court also held that the mere fact that Germany may not have specifically objected to the equidistance principle as contained in Article 6, is not sufficient to state that the principle is now binding upon it.

5. In conclusion, the Court held that Germany had not acted in any manner so as to incur obligations contained in Article 6 of the Geneva Convention. The equidistance–special circumstances rule was not binding on Germany by way of treaty law.

2. Nature of the customary international law obligation: Is Germany bound by the provisions of Article 6 of the Geneva Convention in so far as they reflect customary international law?

6. Netherlands and Denmark argued that Article 6 also reflected ‘the accepted rule of general international law on the subject of continental shelf delimitation’ and that it existed independently of the Convention. Therefore, they argued, Germany is bound by the subject matter of Article 6 by way of customary international law.

7. To decide if the equidistance principle bound Germany by way of customary international law, the Court examined (1) the status of the principle contained in Article 6 as it stood when the Convention was being drawn up; and (2) its status after the Convention came into force.

(a) What was the customary law status of Article 6 at the time of drafting the Convention?

8. The Court held that the principle of equidistance, as contained in Article 6 did not form a part of existing or emerging customary international law at the time of drafting the Convention. The Court supported this finding based on (1) the hesitation expressed by the drafters of the Convention, the International Law Commission, on the inclusion of Article 6 into the Convention and (2) the fact that  reservations to Article 6 was permissible under the Convention. The Court held:

“… Article 6 is one of those in respect of which, under the reservations article of the Convention (Article 12) reservations may be made by any State on signing, ratifying or acceding, – for speaking generally, it is a characteristic of purely conventional rules and obligations that, in regard to them, some faculty of making unilateral reservations may, within certain limits, be admitted; whereas this cannot be so in the case of general or customary law rules and obligations which, by their very nature, must have equal force for all members of the international community, and cannot therefore be the subject of any right of unilateral exclusion exercisable at will by any one of them in its own favor…. The normal inference would therefore be that any articles that do not figure among those excluded from the faculty of reservation under Article 12, were not regarded as declaratory of previously existing or emergent rules of law …” (see para 65 for a counter argument and the Court’s careful differentiation)

(b) Did the provisions in Article 6 on the equidistance principle attain the customary law status after the Convention came into force?

9. The Court then examined whether the rule contained in Article 6 had become customary international law after the Convention entered into force – either due the Convention itself (i.e., if enough States had ratified the Convention in a manner so as to fulfil the criteria specified below), or because of subsequent State practice (i.e. even if an adequate number of States had not ratified the Convention, one could find sufficient State practice to meet the criteria below). The Court held that Article 6 of the Convention had not attained a customary law status. (Compare the 1958 Geneva Convention with the four Geneva Conventions on 1949 relating to international humanitarian law in terms of the latter’s authority as a pronouncement of customary international law).

10. For a customary rule to emerge the Court held that it needed: (1) very widespread and representative participation in the Convention, including States whose interests were specially affected (in this case, they were coastal States) (i.e. generality); and (2) virtually uniform practice (i.e. consistent and uniform usage) undertaken in a manner that demonstrates (3) a general recognition of the rule of law or legal obligation (i.e. opinio juries). In the North Sea Continental Shelf cases the court held that the passage of a considerable period of time was unnecessary (i.e. duration) for the formation of a customary law.

Widespread and representative participation

11. The Court held that the first criteria was not met. The number of ratifications and accessions to the Convention (39 States) were not adequately representative or widespread.


12. The Court held that the duration taken for a customary law rule to emerge is not as important as widespread and representative participation, uniform usage, and the existence of an opinio juris. It held that:

“Although the passage of only a short period of time (in this case, 3 – 5 years) is not necessarily, or of itself, a bar to the formation of a new rule of customary international law on the basis of what was originally a purely conventional rule, an indispensable requirement would be that within the period in question, short though it might be, State practice, including that of States whose interests are specially affected, should have been both extensive and virtually uniform in the sense of the provision invoked and should moreover have occurred in such a way as to show a general recognition that a rule of law or legal obligation is involved.”

Opinio juris

13. Opinio juris is reflected in acts of States (Nicaragua Case) or in omissions (Lotus case), in so far as those acts or omissions were done following a belief that the said State is obligated by law to act or refrain from acting in a particular way. (For more on opinio juris click here).

14. The Court examined 15 cases where States had delimited their boundaries using the equidistance method, after the Convention came into force (paras. 75 -77). The Court concluded that even if there were some State practice in favour of the equidistance principle, the Court could not deduct the necessary opinio juris from this State practice. The North Sea Continental Shelf Cases confirmed that both State practice (the objective element) and opinio juris (the subjective element) are essential pre-requisites for the formation of a customary law rule. This is consistent with Article 38 (1) (b) of the Statute of the ICJ. The Court explained the concept of opinio juris and the difference between customs (i.e. habits) and customary law:

“Not only must the acts concerned amount to a settled practice, but they must also be such, or be carried out in such a way, as to be evidence of a belief that this practice is rendered obligatory by the existence of a rule of law requiring it. The need for such a belief, i.e, the existence of a subjective element, is implicit in the very notion of the opinio juris sive necessitatis. The States concerned must therefore feel that they are conforming to what amounts to a legal obligation. The frequency, or even habitual character of the acts is not in itself enough. There are many international acts, e.g., in the field of ceremonial and protocol, which are performed almost invariably, but which are motivated only by considerations of courtesy, convenience or tradition, and not by any sense of legal duty.” (Para 77).

15.  The Court concluded that the equidistance principle was not binding on Germany by way of treaty or customary international law. In the case of the latter, the principle had not attained a customary international law status at the time of the entry into force of the Geneva Convention or thereafter. As such, the Court held that the use of the equidistance method is not obligatory for the delimitation of the areas concerned in the present proceedings.

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23 thoughts on “North Sea Continental Shelf Cases (Summary)

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