Continental Shelf – Meaning, Principle and Case Laws

By | March 22, 2018
Notes on Continental Shelf

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The concept of continental shelf is mainly co-related with an exploitation of the natural resources from the sea adjacent to the territorial sea. This was one of the important developments after the Second World War in relation to the law of the sea was the evolution and acceptance of the concept of the continental shelf. The President of the United States proclaimed that the natural resources of the continental shelf were ‘beneath the high seas but contiguous to the coasts of the United States as appertaining to the United States and subject to its jurisdiction and control’. The continental shelf was regarded ‘as an extension of the land mass of the coastal nation’. The main reason for this action of the United States was to reserve for itself, the oil and mineral resources in the seabed which had become technologically possible to drill.

Proclamation soon became the trendsetter and was immediately followed by similar unilateral declarations by many maritime nations which laid claims of exclusive jurisdiction control or sovereign rights over the resources of the continental shelf and associated offshore areas. These declarations led to the formation of customary international law giving coastal States jurisdictional rights over their shelves. These rights over the resources of the continental shelf were universally accepted by the 1958 Geneva Convention on the Continental Shelf.

Meaning and Definition

Geologically, the continental shelf may be defined as the zone around the continent extending from the low-water line to the depth, at which there is usually a marked increase of declivity to a greater depth. What is commonly understood by the ‘continental shelf’ is a gently sloping platform of submerged land surrounding the continents and islands. It is a submerged bed of the sea, contiguous to a continental land mass, and found in such a manner as to be really an extension of, or appurtenant to this land mass. Normally, it extends to a depth of approximately 200 meters, at which point the first substantial ‘fall off’ of the seabed occurs. At certain places, it continues beyond a depth of 200 meters.

Definition of Continental Shelf under the Geneva Convention of 1958

In 1958 Continental Shelf Convention used the term ‘continental shelf’ as referring ‘to the seabed and subsoil of the submarine areas adjacent to the coast but outside the area of the territorial sea, to a depth of 200 meters or beyond that limit, to where the depth of the superjacent waters admits of the exploitation of the natural resources of the said areas’. Thus, the shelf has been defined in terms of ‘exploitability; and the depth of the sea. It means that if the exploitation of the resources could be made beyond the limit of 200 meters depth, that area could be claimed by the coastal State as its continental shelf. The requirement of the phrase ‘adjacent of the coast’ is not solely confined to the proximity, but provided the legal basis for the coastal State to claim jurisdiction over the continental shelf.

Definition of Continental Shelf under the Convention on the Law of the Sea, 1982

This Convention has defined the term continental shelf under Para I of Article 76 by stating that the continental shelf of a coastal State comprises the seabed and subsoil of the submarine areas that extend beyond its territorial sea throughout the natural prolongation of its land territory to the outer edge of the continental margin, or to a distance of 200 nautical miles from the baselines from which the breadth of the territorial sea is measured where the outer edge of the continental margin does not extend up to that distance.

Rights of Coastal States over Continental Shelf under UN Convention on the Law of the Sea, 1982

Article 77 of the Convention provides various provisions with regards to the rights of coastal states. The coastal State enjoys limited sovereign rights over the continental shelf for the purpose of exploring and exploiting its ‘natural resources’, and not sovereignty. These rights are exclusive in the sense that no one can undertake these activities without the express consent of the coastal State or make a claim to the continental shelf. They also do not depend on occupation, effective or notional, or any express proclamation.

The ‘natural resources’ of the continental shelf consist of mineral and other non-living resources of the seabed and sub-soil, together with living organisms which at the harvestable stage, either are immobile on or under the seabed or are unable to move except in constant physical contact with the seabed or subsoil.

The coastal State also has the exclusive right to authorize and regulate drilling of the sub-soil for all purposes. [Article 81]  Like the EEZ, the coastal State has the exclusive right to construct, maintain or operate the artificial islands, installations, and structures on the shelf. [Article 80]

Rights of Other States in Continental Shelf under UN Convention on the Law of the Sea, 1982

The Convention also gives various rights to the Other States. The rights of the coastal State over the continental shelf do not affect the legal status of the superjacent waters or of the airspace above those waters. The exercise of the rights of the coastal State over the continental shelf must not infringe or result in any unjustifiable interference with navigation and other rights and freedoms of other States as provided for in this Convention. [Article 78] Also, all States are entitled to lay submarine cables and pipeline on the continental shelf. [Article 79]

Principles and Case Laws

The delimitation of the continental shelf between nations has generated a lot of litigation because of its economic importance. Rules relating to delimitation are provided in Article 6 of the 1958 Continental Shelf Convention and Article 83 of the 1982 Convention.

The delimitation of boundaries remained more contentious between the adjacent States as opposed to the opposite States where the median line was to be followed. In the case of adjacent States, ‘equidistance principle’ was found to be inadequate to demarcate the continental shelf, nor did it represent the customary international law.

Continental Shelf and North Sea Continental Shelf Case

The International Court of Justice, for the first time, has the occasion to determine the adequacy of the rule enshrined in Article 6 in the North Sea Continental Shelf case. In the two separate cases against West Germany filed by the Netherlands and Denmark, the Court was asked to decide about the ‘applicable’ principles and rules of international law ‘to the determination as between the Parties of the areas of the continental shelf in the North Sea which appertain to each of them beyond the partial boundary.

The two cases were joined by the Court. Denmark and the Netherlands argued that the ‘equidistance/special circumstances rule’ in Art. 6 would be applied. Germany instead proposed ‘the doctrine of the just and equitable share’. Germany’s opposition to the ‘equidistance rule’ was based on the fact that the rule, if applied on a concave coastline, such as that of the North Sea, shared by all the three States concerned, would result into giving the State in the middle, and in this case Germany, a smaller continental shelf than it might otherwise obtain.

The Court rejected both these contentions and held that applying the equidistance principle will lead to inequitable results because of the peculiar coastline of the States concerned and opined that the notion of equidistance could not be logically be compulsorily applied in all situations. It is not consonant with certain basic legal notions, ‘those principles being that delimitation must be the object of agreement between the States concerned, and such agreement must be arrived at in accordance with equitable principles.’

Thus, in following the ‘equitable principles’, the factors to be taken into account are:

  • the relevant circumstances, i.e., the geographical situation of the parties and natural configuration of the coast;
  • proportionally, i.e., the extent of the continental shelf areas appertaining to coastal State and the length of the coast measured in the general direction of the coastline; and
  • the concept of natural prolongation, i.e., the shelf is an appurtenant to the land territory.

The approach is taken by the International Court of Justice on the ‘equidistance principle’ has been followed by the Court in Tunisia vs Libya case, the Court was asked to specify principles and rules of international law which were applicable to the delimitation of the continental shelf between Tunisia and Libya. They have a single continental shelf as the natural prolongation of their land territory, and hence no principle of ‘natural prolongation’ as such could be applied. The Court observed that since the two countries abutted on a common continental shelf, the physical criterion was of no assistance for the purpose of delimitation. The application of the equidistance method could not, in particular circumstances of the case, lead to an equitable result, and in such a case, the delimitation can be effected on the basis of ‘equitable principles’, taking into account all the relevant circumstances.

Libya vs Malta case

The Libya vs Malta was the first case decided by the Court a fatter signing of the 1982 Convention. Though both the States were signatories to the Convention, they agreed for the dispute to be governed by customary international law. The Court, however, looked into the provisions of the Convention as a rule of customary international law, and observed that ‘the principles and rules, applicable to the delimitation of continental shelf areas are those which are appropriate to bring about an equitable result.’ In deciding the dispute, the Court placed great reliance on the ‘equidistance principle’. But to achieve an equitable result, it will be necessary to first draw a line, every point of which should be equidistant from the coast of the two opposite States concerned and then to make adjustments in the light of all the relevant circumstances. The Court once again discounted the ‘natural prolongation’ factor propounded in the North Sea Continental Shelf cases, which was subservient to the equitable principle.

Thus, the judicial practice has clearly established that the principle of equidistance is not an applicable rule in all cases of delimitation between adjacent States. The ‘natural prolongation’ criterion has similarly given way to distance criterion (i.e. 200 nautical miles from the coast). The emphasis on ‘equitable solution’ in the 1982 Convention, however, is without any accompanying procedure to be followed to achieve it. The application of equitable principle reduces the chances of settling boundary disputes without litigation.

Continental Shelf

Extended continental shelf constraint lines. A country may use either constraint line to define the outer continental shelf: either 350 nautical miles seaward of the baseline, or 100 nautical seaward of the 2,500 meter depth contour (isobath). Source – U.S. Department of Commerce


Indian Position on Continental Shelf

The Maritime Zones Act, states the Indian position. India has proclaimed 200 nautical miles from the baselines as its continental shelf. The rights and duties of Indian in this regime are similar to other States, as specified in the international Conventions. However, the government can declare the area of the continental shelf and its superjacent waters as designated areas and make provisions for regulating it.

Continental Shelf and EEZ

The regimes of continental shelf and EEZ co-exist under the customary international law and the 1982 Convention. They contain few significant similarities and differences. The coastal State enjoys sovereign rights over the resources of the EEZ and the continental shelf. These rights are primarily of an economic kind and the area otherwise pertains to the high seas. The traditional freedoms of the high seas under the customary international law, i.e., freedoms of navigation, overflight and immersion and available to other nations in these zones.

However, they are different in many ways:

  1. Whereas the coastal State gets rights over the continental shelf because of its land territory, i.e., continental shelf accrues to it under the customary international law, the EEZ is a concept of law, whereas continental shelf is a concept of geography.
  2. Whereas the rights of continental shelf can exist beyond the limit of 200 miles from the coast whereas shelf and margin extend beyond that limit, it is not so with the EEZ.
  3. The resources of the EEZ are subject to the rule of sharing the surplus of the living resources of the EEZ with other nations, particularly with landlocked and geographically disadvantageous States, but the resources of the continental shelf are immune from this requirement and if the coastal State does not exploit them, no other State has a right to do so.
  4. The continental regime applies to shelf resources of States that have claimed an EEZ as well as States that have not done so and applies to the shelf resources beyond the 200 nautical mile limit. Thus, under the 1982 Convention, a continental shelf can exist without EEZ, but there cannot be an EEZ without a corresponding continental shelf.

In Libya vs. Malta Case, the Court was of the view that both the regimes are linked together, ‘since the rights enjoyed by a State over its continental shelf would also be possessed by it over the seabed and sub-soil of any exclusive economic zone which it might proclaim.’

Author – Mayank Shekhar


  1. Dr. H.O. Agarwal, International Law, 21st Edition, 2016

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Author: Mayank Shekhar

Mayank is a student at Faculty of Law, Delhi University. Under his leadership, Legal Bites has been researching and developing resources through blogging, educational resources, competitions, and seminars.