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data can define them only approximately (as lying in the vicinity of the 2500-metre isobath (see p. 8, ante) but 3000 metres or 3500 metres could be suggested alternatively.

(c) The legal limits of the continental shelf.-If the views of the International Court of Justice in the North Sea Cases are accepted as being declaratory of the underlying notion contained in art. 1 of the Geneva Convention on the Continental Shelf, that the continental shelf is "an area physically extending the territory of most coastal States", or that it is "the natural prolongation or continuation of the land territory... of the coastal State", then the question arises whether the legal cut-off point of the coastal State's "sovereign rights" would correspond with the geographical terminating contour of the continental shelf.

The Court did not indicate how far, in its view, the continental shelf in a legal sense extends. But, if the Court meant to equate the expression "natural prolongation" with the geophysical structure of the continental margin, then the maximum extent to which "sovereign rights" can be pressed would be the base of the continental slope, or even the continental rise. Such sovereign rights do not so extend immediately or inherently beyond the 200-metre isobath. They could only extend pursuant to the "exploitability criterion in art. 1. If, on the other hand, the "exploitability" criterion is not a matter of customary international law, then it would be arguable that, for States which are not parties to the Convention, sovereign rights inhere in coastal States to the full extent of the natural prolongation of their land masses. Such States would not, on this argument, be bound by a 200metre limitation, and would not need to rely on exploitability in order to manifest sovereign rights over the total area of natural prolongation. The questions so posed immediately raise problems of definition, since the morphological nature and the limits of the continental shelf in relation to the coastal State from which it stems are matters which can only be determined with any accuracy in the course of time as technology develops to the point of being able to fix the actual boundary. Until this stage is reached, discussion of the deep sea bed, except in depths at which the continental shelf may reasonably be presumed to be non-existent, can only take place in a vacuum, and for this reason a note of caution is urged by the Committee that the fixing of a purely arbitrary limit to the continental shelf should be resisted until more evidence is available on the nature of the outer continental shelf. The problem posed for legal analysis is that embodied in what has become known as "the exploitability" criterion in art. 1, which reads as follows:

"For the purpose of these Articles, the term 'continental shelf' is used as referring (a) to the sea bed and subsoil of the submarine areas adjacent to the coast but outside the area of the territorial sea, to a depth of 200 metres or, beyond that limit, to where the depth of the superjacent waters admits of the exploitation of the natural resources of the said areas; (b) to the sea bed and subsoil of similar submarine areas adjacent to the coasts of islands."

At least for parties to the Convention, the exercise of a coastal State's "sovereign rights" beyond the 200-metre isobath is dependent on a test of "exploitability" within the meaning of art. 1. The term "admits of" linked to exploitability rather than to exploration tends to import something more than a mere feasibility of recovering natural resources. If it means nothing more than this, then a substantial part of all the continental shelves of the world are already subject to "sovereign rights" and the reference to a 200-metre isobath in art. 1 is meaningless. Any limitation upon the extension of "sovereign rights" over the continental shelf beyond the 200-metre isobath can accordingly only derive from the view that "admits of" implies practicable exploitation rather than abstract potential to exploit. If the legitimate extension of "sovereign rights" to areas beyond the 200-metre isobath had to await proof which only exploration drilling could provide, the stage of exploration would be one of legal vacuum. But since explorers require a guarantee of legal security before making the investment necessary to furnish such proof, a vicious circle is created by this interpretation of art. 1.

The Committee considers that there has been insufficient recognition given in most discussions of art. 1 to the dilemma facing both Governments and industry, and that clarification, not only of the limits of the exploitability criterion itself, but also of the specific instances in which the criterion may be required, is of first importance.

The Committee feels that any interpretation should be resisted, which implies that the limitations on the exercise of "sovereign rights" over the continental shelf beyond the 200-metre isobath should be based on economic rather than technical feasibility to exploit. We believe that the idea which should be conveyed is that of “extraction" rather than exploitation, and, if any amendment of the Continental Shelf Convention is to be made, the substitution in art. 1 of the phrase "admits of the exploitation..." by "admits of the extraction" provides an acceptable solution to the problems adverted to in this report which arise through the use of the term "exploitation". The effect of this would be that the extension of "sovereign rights" over the continental shelf would be limited to those depths at which it may be technically feasible to extract the natural resources belonging to the coastal State.

It is important that a clear distinction be made between the ability to explore by drilling for a natural resource and the ability to extract that resource. It is not intended that the technical ability to explore alone should be the determining factor. For example, in the case of petroleum exploration, although it is presently technically possible to explore and take samples in water depths of up to 18,000 feet, extraction of petroleum is presently possible only in much more limited depths. Major changes in technique will be necessary before extraction of petroleum becomes technically possible in water depths beyond about 1500 feet-for example, diver capability for servicing sub-surface equipment and changes in the marine conductor to permit re-entry of the hole with new drilling bits and to control the well. It is considered

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that the main feature of the test which has been advocated should be that it should be technically feasible to produce at a specified depth, on the scale that will enable it to be processed, as distinct from an experimental scale. The disadvantages in advancing economic feasibility as the test are as has been shown earlier that it may not operate with equal fairness between States. Whilst not all coastal States may have the finance or the capability to develop techniques to drill and extract at depth it is intended that the "extraction" test should operate to give all States the right to exercise "sovereign rights" over their continental shelf at the depth at which it may from time to time be determined that extraction is technically feasible.

Since technical development of extraction techniques is likely to remain sufficiently far ahead of the exploration techniques which may economically be utilized by industry, the "extraction" test should enable States to grant exclusive exploration rights to industry sufficiently in advance of the time when exploitability may become a practical and economic possibility.

It does not follow that the "extraction" criterion can validate an extension of "sovereign rights" beyond the morphological structure of the continental margin. Implied in that formula, the Committee believes, is the potentiality to expand “sovereign rights" as far as the continental margin extends, although it is recognized that at the present moment some contour line on the declivity of the continental shelf may be the actual boundary of "sovereign rights". As it becomes technically feasible to extract from the entire continental shelf, the limit of "sovereign rights" becomes the limit of the continental margin itself.

(d) Australian practice.-The Australian Government has taken the "exploitability" criterion to imply a flexible and expanding boundary to the coastal State's rights under the sea, and this view was expressed by the Attorney-General in the second reading of the Petroleum (Submerged Lands) Bill. He said:

"The outer limit is determined as the point where it is possible with your capacity to go to exploit resources. This capacity will increase with technical advancement and thus the limits advance outwards. The outer limit today may not be the outer limit tomorrow. This presents the draftsmen of an Act such as this with a problem. The Bill was drafted on the basis of application to 'areas'. The device adopted was to draw the series of 'pictureframes' that honourable members will see in the maps contained in the booklet which has been distributed. The legislation makes it clear, and this is recognized by notations on the maps themselves, that the legislation will apply only to so much of the submerged lands within a particular frame as has the character either of territorial sea bed or of continental shelf within the meaning of the convention with its varying limits."

The areas designated vary with respect to both extent and depth, and off New South Wales, for example, go far beyond the continental shelf and embrace Lord Howe Island. Within these areas the petroleum legislation operates in respect of so much of the exploitation of the sea bed as comes within the scope of the Geneva Convention. The idea

of an expanding continental shelf boundary is thus imported into the operation of the legislation.

(e) Australian islands and reefs.-Australia has legislated separately with respect to petroleum activities for two groups of coral islands (see Appendix). The Ashmore and Cartier Islands are situated on the edge of the continental shelf (about 150 miles to the north-west of Australia) and are part of it. The Willis Group and certain other Coral Sea Islands are situated on the "Queensland Plateau". This large area, now being studied by marine geologists and geophysicists, is generally below accepted shelf depth and is separated from the Great Barrier Reef, and thus from the North Queensland continental shelf, by a narrow channel some 1000-1500 metres deep. It could be considered to stand in a similar relationship to the Queensland coast as the part of the North Sea which is "adjacent" to Norway, where a narrow “trough" separates the two areas.

Over the entire length of the Queensland coast, the shallow offshore shelf, which terminates at the Barrier Reef, slopes down to depths of 1000 metres. From Torres Strait at the northern end of Queensland to latitude 18° south (about Townsville) this slope is very steep. South of this latitude the 1000-metre contour extends as far as 120 miles seawards after which the slope again becomes very steep. In the middle, about latitude 17° south, the sea bed rises again offshore to an extensive bank of less than 1000 metres in depth containing several islets and reefs, including the Willis and Coringa islets. This bank rises quite gently out of depths not exceeding 2000 metres and measures about 240 miles by 120 miles. Further south several islets and reefs rise exceedingly steeply from greater depths, each amounting to a super-surface seamount at least 1000 metres high. The extent of the reefs above sea level is of the order of 10 to 15 miles in diameter. One such "seamount" is Cato Island.

The Ashmore and Cartier Islands are deemed by the Ashmore and Cartier Islands Acceptance Act to form part of the Northern Territory of Australia. The Petroleum (Ashmore and Cartier Islands) Act 1967 extended the Petroleum (Submerged Lands) Act 1967 of the Commonwealth of Australia to the Territory of Ashmore and Cartier and deemed the islands and reefs themselves to be "submerged land" for the purposes of the administration of the petroleum legislation.

The Coral Sea Islands Acts 1969 provides for the government of the Coral Sea Islands for the purpose of further legislation respecting the continental shelf of these islands.

The question of the continental shelves of islands is dealt with in art. 1 of the Geneva Convention:

"... the term 'continental shelf' is used as referring... (b) to the sea bed and subsoil of similar submarine areas adjacent to the coasts of islands."

Here the question that arises is whether the expression “adjacent to" involves the idea of the natural prolongation of the supersurface relief to the terminating point of the geophysical structure. When there are

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neighbouring States this may give rise to difficult questions of delimitation, especially when the islands are small.

The question whether the expression "islands" in the Continental Shelf Convention is the same as the expression "islands" in the Convention on the Territorial Sea and Contiguous Zone has not been discussed. It is arguable that the only relevant question is that of political sovereignty over the superjacent feature, in virtue of which the seabed becomes subject to sovereign rights. But it is also arguable that the sea bed must be the natural prolongation of the land mass, and the question arises whether a coral cay is the natural extension of the sea bed rather than vice versa.

Whether an area of islands such as the Queensland Plateau is a prolongation of the shelf adjacent to the continent, notwithstanding its separation from it by an area of deeper water, is a matter of geological (geophysical) argument. Geologically speaking, island-studded platforms or island chains could well be considered as prolongations of the land where the separating trench or trough is (a) of minor extent, (b) of geologically recent origin, and (c) does not form a boundary between geologically distinct areas. The legal significance of similarity of geological structure on a sub-continental scale is, however, questionable.

III The deep sea bed

(a) The present law relating to deep sea bed activities outside the continental shelf.-There have been several instances in history of States acquiring exclusive rights over the living natural resources of the sea bed beyond their territorial waters, and in the Behring Sea Arbitration some judicial recognition was given to these as instances of rather than exceptions to international law. However, all these cases concerned areas which are now subsumed under the category of the continental shelf as a legal concept, so that they afford little direct precedent for exclusive rights over the deep sea bed activities.

The Permanent Court of International Justice in the case of the SS "Lotus" took the view that a State may act in absence of a prohibitive rule of international law, and this principle may be applied to activities on the sea bed of the deep ocean. There is no international law principle prohibiting exploration and exploitation of the mineral resources of the deep sea bed, provided reasonable regard is had for the interests of other States in the exercise of their freedoms of the high

seas.

There would seem to be two possible modes of utilization of the sea bed.

(i) Structures might be erected on the sea bed so that it could be said that specific spots on the sea bed could be effectively occupied. But the radius of sovereignty from such structures would seem to be minimal and the present international atmosphere is not conducive to the effective creation of exclusive "zones of interest" such as resolved this type of problem on land during the era of colonial development.