Continental shelf, high seas and the deep seabed

1. The continental shelf: origin

Geologically, the continental shelf is the gently sloping submerged extension of the land mass before the steep continental slope descends to the ocean floor. The legal concept began with the Truman Proclamation of 28 September 1945, by which the US claimed jurisdiction and control over the natural resources of the subsoil and seabed of the continental shelf contiguous to its coasts, while leaving the waters above as high seas. Other States made similar claims, and the Geneva Convention on the Continental Shelf, 1958, codified the doctrine, defining the shelf by a 200-metre depth or exploitability test.

2. Definition under UNCLOS

Article 76(1): 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 where the outer edge of the margin does not extend up to that distance.

• Every coastal State has a shelf of at least 200 nautical miles, whatever the geology.
• Where the margin extends further, the outer limit may not exceed 350 nautical miles from the baseline or 100 nautical miles from the 2,500-metre isobath (Article 76(5)).
• A State claiming beyond 200 miles must submit particulars to the Commission on the Limits of the Continental Shelf, whose recommendations make the limits final and binding (Article 76(8)). India has made such a submission.

3. Rights of the coastal State

Article 77:

• The coastal State exercises over the shelf sovereign rights for the purpose of exploring it and exploiting its natural resources.
• The rights are exclusive: if the coastal State does not explore or exploit, no one may do so without its express consent.
• The rights do not depend on occupation, effective or notional, or on any express proclamation. They exist ipso facto and ab initio.
• Natural resources mean mineral and other non-living resources of the seabed and subsoil, and sedentary species (organisms that at the harvestable stage are immobile on or under the seabed or move only in constant physical contact with it, such as oysters and pearls).

Limits: the rights do not affect the legal status of the waters above or the airspace (Article 78); other States may lay submarine cables and pipelines, subject to reasonable measures (Article 79); the coastal State has exclusive rights over artificial islands and drilling (Articles 80 and 81); and it must make payments to the International Seabed Authority for exploitation beyond 200 miles (Article 82).

4. North Sea Continental Shelf cases

North Sea Continental Shelf (Federal Republic of Germany v. Denmark; Federal Republic of Germany v. Netherlands), ICJ, 1969. Because the German coast is concave, the equidistance method in Article 6 of the 1958 Convention would have given Germany a small triangle of shelf. Germany had signed but not ratified that Convention. The Court held:

• Article 6 did not bind Germany as a treaty, and the equidistance principle had not become customary law (the Court's test for treaty rules passing into custom is in the note on sources);
• the coastal State's rights over the shelf exist ipso facto and ab initio by virtue of its sovereignty over the land, as its natural prolongation;
• delimitation must be effected by agreement in accordance with equitable principles, taking account of all relevant circumstances, including the configuration of the coasts and a reasonable degree of proportionality between the shelf area and the length of coastline.

Article 83 of UNCLOS now provides that delimitation between States with opposite or adjacent coasts shall be effected by agreement on the basis of international law in order to achieve an equitable solution. The ICJ's modern method (Maritime Delimitation in the Black Sea, Romania v. Ukraine, 2009) is: draw a provisional equidistance line, adjust it for relevant circumstances, then check for disproportion. The arbitral tribunal applied this method between India and Bangladesh in the Bay of Bengal Maritime Boundary Arbitration (2014).

5. The high seas

Article 86: the provisions on the high seas apply to all parts of the sea not included in the EEZ, the territorial sea or internal waters of a State, or the archipelagic waters of an archipelagic State. Article 89: no State may validly purport to subject any part of the high seas to its sovereignty. Article 88: the high seas are reserved for peaceful purposes.

Freedoms of the high seas (Article 87). The high seas are open to all States, coastal or land-locked. Freedom of the high seas comprises, among others:

• (a) freedom of navigation;
• (b) freedom of overflight;
• (c) freedom to lay submarine cables and pipelines, subject to Part VI;
• (d) freedom to construct artificial islands and other installations permitted under international law, subject to Part VI;
• (e) freedom of fishing, subject to the conditions on conservation in Section 2 of Part VII;
• (f) freedom of scientific research, subject to Parts VI and XIII.

These freedoms must be exercised with due regard for the interests of other States (Article 87(2)). The list is not exhaustive (“inter alia”); the 1958 Convention had listed only the first four.

6. Jurisdiction on the high seas

• Flag State. Every State fixes the conditions for granting its nationality to ships; there must be a genuine link between the State and the ship (Article 91). Ships sail under one flag and are subject to its exclusive jurisdiction on the high seas (Article 92). The flag State must effectively exercise jurisdiction and control in administrative, technical and social matters (Article 94). M/V Saiga (No. 2) (Saint Vincent and the Grenadines v. Guinea), ITLOS, 1999, held that the genuine-link requirement does not allow other States to refuse to recognise the flag.
• Collisions: only the flag State or the State of nationality may prosecute (Article 97, reversing Lotus).
• Piracy (Article 101): any illegal act of violence, detention or depredation committed for private ends by the crew or passengers of a private ship or aircraft on the high seas against another ship or aircraft or persons or property on board. Every State may seize a pirate ship and its courts may decide the penalties (Article 105). India enacted the Maritime Anti-Piracy Act, 2022.
• Right of visit (Article 110): a warship may board a foreign ship if there is reasonable ground for suspecting piracy, slave trade, unauthorised broadcasting, absence of nationality, or a false flag.
• Hot pursuit (Article 111): the coastal State may pursue a foreign ship that has violated its laws, if the pursuit begins while the ship is within its internal waters, territorial sea, contiguous zone or EEZ (for violations relevant to that zone), is continuous and uninterrupted, follows a visual or auditory signal to stop, and is carried out by warships or clearly marked government ships or aircraft. It ends when the ship enters the territorial sea of its own or a third State. In The I'm Alone (Canada v. USA, 1935) the sinking of a Canadian rum-runner was held unjustified, since only necessary and reasonable force is permitted.

7. The deep seabed (the Area)

The seabed and ocean floor beyond the limits of national jurisdiction is the Area (Article 1). The Area and its resources are the common heritage of mankind (Article 136); no State may claim sovereignty over it (Article 137); activities are organised through the International Seabed Authority for the benefit of mankind as a whole, with special regard to developing States (Article 140). The 1994 Implementation Agreement modified Part XI to meet the objections of industrialised States. The 2023 Agreement on Marine Biological Diversity of Areas beyond National Jurisdiction (the BBNJ or High Seas Treaty) adds rules on marine genetic resources and protected areas beyond national jurisdiction.

How this is examined

The freedoms question is a six-mark note: Article 86 definition, Article 87 list with all six freedoms, “due regard”, Article 89, and a line on the limits (piracy, visit, hot pursuit). The continental shelf essay: Truman Proclamation, Article 76 definition with the 200 and 350 mile limits, Article 77 rights, the limits in Articles 78 to 82, then North Sea and Article 83. Where territorial sea and continental shelf are set together, contrast them: sovereignty over water, airspace and bed in the first; sovereign rights over seabed resources only in the second.