(Customary international law; principles applicable in the delimitation of continental
shelf)
37. For both Parties, the starting point for a discussion of the applicable principles and
rules has been the Court’s Judgment of 20 February 1969 in the North Sea Continental SheIf
cases. The Parties both take the view that, as in those cases, the delimitation in the present
case has to be effected
“by agreement in accordance with equitable principles, and taking account of all
the relevant circumstances, in such a way as to leave as much as possible to each
Party all those parts of the continental shelf that constitute a natural prolongation of
its land territory into and under the sea, without encroachment on the natural
prolongation of the land territory of the other”,
and that among the factors to be taken into account in the negotiations contemplated
between the Parties was
“the element of a reasonable degree of proportionality . . . between the extent of
the continental shelf areas appertaining to the coastal State and the length of its coast
measured in the general direction of the coastline” (I.C.J. Reports 1969, pp. 53-54,
para. 101 (C) (1) and (D) (3)).
38. The present case however illustrates how the application of the principles and rules
enunciated, and the factors indicated, by the Court in 1969 may lead to widely differing
results according to the way in which those principles and rules are interpreted and applied,
and the relative weight given to each of those factors in determining the method of
delimitation. Yet here also the Parties are, to a lesser extent, in accord: for both Parties it is
the concept of the natural prolongation of the land into and under the sea which is
commanding. Where they differ in this respect is first, as to the meaning of the expression
“natural prolongation”, that is to say by reference to what terrestrial unit (continental
landmass or State territory), and by the application of what criteria, it is to be determined
whether a given area is the natural prolongation of the one State or of the other. Secondly,
while there is also broad agreement between the Parties that a delimitation which leaves as
much as possible to each State those parts of the continental shelf that constitute its natural
prolongation will necessarily be in accordance with equitable principles, they differ in
particular as to the extent to which considerations other than the dictates of geography,
geomorphology and geology – and specifically considerations of equity – operate to determine
what is the natural prolongation of each State.
41. Both Parties consider that the “continental shelf” is an institution of international law
which, while it remains linked to a physical fact, is not to be identified with the phenomenon
designated by the same term – “continental shelf” – in other disciplines. It was the continental
shelf as “an area physically extending the territory of most coastal States into a species of
platform” which “attracted the attention first of geographers and hydrographers and then of
140
jurists” (I. C. J. Reports 1969, p. 5 1, para. 95); but the Court notes that at a very early stage in
the development of the continental shelf as a concept of law, it acquired a more extensive
connotation, so as eventually to embrace any sea-bed area possessing a particular relationship
with the coastline of a neighbouring State, whether or not such area presented the specific
characteristics which a geographer would recognize as those of what he would classify as
“continental shelf”. This widening of the concept for legal purposes, evident particularly in
the use of the criterion of exploitability for determining the seaward extent of shelf rights, is
clearly apparent in the records of the International Law Commission and other travaux
préparatoires of the 1958 Geneva Convention on the Continental Shelf.
42. It will be recalled that the definition of the continental shelf in Article 1 of the 1958
Convention is as follows:
“For the purpose of these articles, the term ‘continental shelf’ is used as referring
(a) 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 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 seabed and subsoil of similar submarine areas adjacent to
the coasts of islands.”
While the 200-metre limit was chosen partly as corresponding approximately to the
normal outer limit of the shelf in the physical sense, the definition of the outer limit of the
shelf by reference to the possibility of exploitation of the sea-bed is clearly open-ended, and
emphasizes the lack of identity between the legal concept of the continental shelf and the
physical phenomenon known to geographers by that name. This definition, which was
according to its terms expressed to be for the purpose of a convention text, was considered by
the Court in its 1969 Judgment to have been one of those regarded in 1958 as “reflecting, or
as crystallizing, received or at least emergent rules of customary law relative to the
continental shelf” (I. C.J. Reports 1969, p. 39, para. 63). The fact that the legal concept, while
it derived from the natural phenomenon, pursued its own development, is implicit in the
whole discussion by the Court in that case of the legal rules and principles applicable to it.
43. It was the Court itself in its 1969 Judgment which gave currency to the expression
“natural prolongation” as part of the vocabulary of the international law of the sea. It should,
however, first be recalled that the geographical and other physical circumstances of that case
were different from those of the present case. In particular the whole relevant area of the
North Sea consisted of continental shelf at a depth of less than 200 metres. Secondly, it
should be borne in mind that, as the Court itself made clear in that Judgment, it was engaged
in an analysis of the concepts and principles which in its view underlay the actual practice of
States which is expressive, or creative, of customary rules. The concept of natural
prolongation thus was and remains a concept to be examined within the context of customary
law and State practice. While the term “natural prolongation” may have been novel in 1969,
the idea to which it gave expression was already a part of existing customary law as the basis
of the title of the coastal State. The Court also attributed to that concept a certain role in the
delimitation of shelf areas, in cases in which the geographical situation made it appropriate to
do so. But while the idea of the natural prolongation of the land territory defined, in general
141
terms, the physical object or location of the rights of the coastal State, it would not necessarily
be sufficient, or even appropriate, in itself to determine the precise extent of the rights of one
State in relation to those of a neighbouring State.
44. Both Parties to the present case have in effect based their argument upon the idea that
because a delimitation should, in accordance with the Judgment in the North Sea Continental
Shelf cases, leave to each Party “all those parts of the continental shelf that constitute a
natural prolongation of its land territory into and under the sea” (I. C.J. Reports 1969, p. 53,
para. 101 (C) (I)), therefore the determination of what constitutes such natural prolongation
will produce a correct delimitation. The Court in 1969 did not regard an equitable delimitation
and a determination of the limits of “natural prolongation” as synonymous, since in the
operative clause of its Judgment, just quoted, it referred only to the delimitation being
effected in such a way as to leave “as much as possible” to each Party the shelf areas
constituting its natural prolongation. The Court also clearly distinguished between a principle
which affords the justification for the appurtenance of an area to a State and a rule for
determining the extent and limits of such area: “the appurtenance of a given area, considered
as an entity, in no way governs the precise delimitation of its boundaries” (I.C.J. Reports
1969, p. 32, para. 46). The Court is therefore unable to accept the contention of Libya that
“once the natural prolongation of a State is determined, delimitation becomes a simple matter
of complying with the dictates of nature”. It would be a mistake to suppose that it will in all
cases, or even in the majority of them, be possible or appropriate to establish that the natural
prolongation of one State extends, in relation to the natural prolongation of another State, just
so far and no farther, so that the two prolongations meet along an easily defined line. Nor can
the Court approve the argument of Tunisia that the satisfying of equitable principles in a
particular geographical situation is just as much a part of the process of the identification of
the natural prolongation as the identification of the natural prolongation is necessary to satisfy
equitable principles. The satisfaction of equitable principles is, in the delimitation process, of
cardinal importance, as the Court will show later in this Judgment, and identification of
natural prolongation may, where the geographical circumstances are appropriate, have an
important role to play in defining an equitable delimitation, in view of its significance as the
justification of continental shelf rights in some cases; but the two considerations – the
satisfying of equitable principles and the identification of the natural prolongation – are not to
be placed on a plane of equality.
45. Since the Court gave judgment in the North Sea Continental Shelf cases, a period has
elapsed during which there has been much State practice in this field of international law, and
it has been under very close review, particularly in the context of the Third United Nations
Conference on the Law of the Sea. The term “natural prolongation” has now made its
appearance in Article 76 of the draft Convention on the Law of the Sea. At this point, the
Court must thus turn to the question whether principles and rules of international law
applicable to the delimitation may be derived from, or may be affected by, the “new accepted
trends” which have emerged at the Third United Nations Conference on the Law of the Sea.
47. Article 76 and Article 83 of the draft convention are the provisions of the draft
convention prepared by the Conference which may be relevant as incorporating new accepted
trends to be taken into account in the present case. According to Article 76, paragraph 1, “the
142
continental shelf of a coastal State comprises the sea-bed 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.” That definition consists of two parts,
employing different criteria. According to the first part of paragraph 1 the natural
prolongation of the land territory is the main criterion. In the second part of the paragraph, the
distance of 200 nautical miles is in certain circumstances the basis of the title of a coastal
State. The legal concept of the continental shelf as based on the “species of platform” has thus
been modified by this criterion. The definition in Article 76, paragraph 1, also discards the
exploitability test which is an element in the definition of the Geneva Convention of 1958.
48. The principle that the natural prolongation of the coastal State is a basis of its legal
title to continental shelf rights does not in the present case, as explained above, necessarily
provide criteria applicable to the delimitation of the areas appertaining to adjacent States. In
so far as Article 76, paragraph 1, of the draft convention repeats this principle, it introduces
no new element and does not therefore call for further consideration. In so far however as the
paragraph provides that in certain circumstances the distance from the baseline, measured on
the surface of the sea, is the basis for the title of the coastal State, it departs from the principle
that natural prolongation is the sole basis of the title. The question therefore arises whether
the concept of the continental shelf as contained in the second part of the definition is relevant
to the decision of the present case. It is only the legal basis of the title to continental shelf
rights – the mere distance from the Coast – which can be taken into account as possibly having
consequences for the claims of the Parties. Both Parties rely on the principle of natural
prolongation: they have not advanced any argument based on the “trend” towards the distance
principle. The definition in Article 76, paragraph 1, therefore affords no criterion for
delimitation in the present case
61. The conclusion which, in the Court’s view, has ineluctably to be drawn from this
analysis is that, despite the confident assertions of the geologists on both sides that a given
area is “an evident prolongation” or “the real prolongation” of the one or the other State, for
legal purposes it is not possible to define the areas of continental shelf appertaining to Tunisia
and to Libya by reference solely or mainly to geological considerations. The function of the
Court is to make use of geology only so far as required for the application of international
law. It is of the view that what must be taken into account in the delimitation of shelf areas
are the physical circumstances as they are today; that just as it is the geographical
configuration of the present-day coasts, so also it is the present-day sea-bed, which must be
considered. It is the outcome, not the evolution in the long-distant past, which is of
importance.
70. Since the Court considers that it is bound to decide the case on the basis of equitable
principles, it must first examine what such principles entail, divorced from the concept of
natural prolongation which has been found not to be applied for purposes of delimitation in
this case. The result of the application of equitable principles must be equitable. This
terminology, which is generally used, is not entirely satisfactory because it employs the term
equitable to characterize both the result to be achieved and the means to be applied to reach
143
this result. It is, however, the result which is predominant; the principles are subordinate to
the goal. The equitableness of a principle must be assessed in the light of its usefulness for the
purpose of arriving at an equitable result. It is not every such principle which is in itself
equitable; it may acquire this quality by reference to the equitableness of the solution. The
principles to be indicated by the Court have to be selected according to their appropriateness
for reaching an equitable result. From this consideration it follows that the term “equitable
principles” cannot be interpreted in the abstract; it refers back to the principles and rules
which may be appropriate in order to achieve an equitable result. This was the view of the
Court when it said, in its Judgment of 1969:
“it is a truism to say that the determination must be equitable, rather is the
problem above all one of defining the means whereby the delimitation can be carried
out in such a way as to be recognized as equitable” (I. C.J. Reports 1969, p. 50, para.
92).
71. Equity as a legal concept is a direct emanation of the idea of justice. The Court whose
task is by definition to administer justice is bound to apply it. In the course of the history of
legal systems the term “equity” has been used to define various legal concepts. It was often
contrasted with the rigid rules of positive law, the severity of which had to be mitigated in
order to do justice. In general, this contrast has no parallel in the development of international
law; the legal concept of equity is a general principle directly applicable as law. Moreover,
when applying positive international law, a court may choose among several possible
interpretations of the law the one which appears, in the light of the circumstances of the case,
to be closest to the requirements of justice. Application of equitable principles is to be
distinguished from a decision ex aequo et bono. The Court can take such a decision only on
condition that the Parties agree (Art. 38, para. 2, of the Statute), and the Court is then freed
from the strict application of legal rules in order to bring about an appropriate settlement. The
task of the Court in the present case is quite different: it is bound to apply equitable principles
as part of international law, and to balance up the various considerations which it regards as
relevant in order to produce an equitable result. While it is clear that no rigid rules exist as to
the exact weight to be attached to each element in the case, this is very far from being an
exercise of discretion or conciliation; nor is it an operation of distributive justice.
72. The Court has thus examined the question of equitable principles, which, besides
being mentioned in the Special Agreement as the first of the three factors to be taken into
account, are, as the Court has emphasized, of primordial importance in the delimitation of the
continental shelf; it has also dealt with the third of the factors mentioned in the Special
Agreement, the “new accepted trends” in the Third Conference on the Law of the Sea. The
second factor must now be considered, that of the “relevant circumstances which characterize
the areà”; and again, it is not merely because they are mentioned in the Special Agreement
that the Court must have regard to them. It is clear that what is reasonable and equitable in
any given case must depend on its particular circumstances. There can be no doubt that it is
virtually impossible to achieve an equitable solution in any delimitation without taking into
account the particular relevant circumstances of the area. Both Parties recognize that equitable
principles dictate that “the relevant circumstances which characterize the area” be taken into
account, but differ as to what they are. The Special Agreement moreover confers on the Court
144
the task of ascertaining what are the relevant circumstances and assessing their relative weight
for the purpose of achieving an equitable result. It is evident that the first and most essential
step in this respect is to determine with greater precision what is the area in dispute between
the Parties and what is the area which is relevant to the delimitation.
73. It should first be recalled that exclusive rights over submarine areas belong to the
coastal State. The geographic correlation between coast and submerged areas off the coast is
the basis of the coastal State’s legal title. As the Court explained in the North Sea Continental
Shelf cases the continental shelf is a legal concept in which “the principle is applied that the
land dominates the sea” (I. C. J. Reports 1969, p. 5 1, para. 96). In the Aegean Sea
Continental Shelf case the Court emphasized that
“it is solely by virtue of the coastal State’s sovereignty over the land that rights of
exploration and exploitation in the continental shelf can attach to it, ipso jure, under
international law. In short, continental shelf rights are legally both an emanation from
and an automatic adjunct of the territorial sovereignty of the coastal State.” (I.C.J.
Reports 1978, p. 36, para. 86.)
As has been explained in connection with the concept of natural prolongation, the coast
of the territory of the State is the decisive factor for title to submarine areas adjacent to it.
Adjacency of the sea-bed to the territory of the coastal State has been the paramount criterion
for determining the legal status of the submerged areas, as distinct from their delimitation,
without regard to the various elements which have become significant for the extension of
these areas in the process of the legal evolution of the rules of international law.
74. The coast of each of the Parties, therefore, constitutes the starting line from which one
has to set out in order to ascertain how far the submarine areas appertaining to each of them
extend in a seaward direction, as well as in relation to neighbouring States situated either in
an adjacent or opposite position. The only areas which can be relevant for the determination
of the claims of Libya and Tunisia to the continental shelf in front of their respective coasts
are those which can be considered as lying either off the Tunisian or off the Libyan coast.
These areas form together the area which is relevant to the decision of the dispute. The area in
dispute, where one claim encroaches on the other, is that part of this whole area which can be
considered as lying both off the Libyan coast and off the Tunisian coast.
75. Nevertheless, for the purpose of shelf delimitation between the Parties, it is not the
whole of the coast of each Party which can be taken into account; the submarine extension of
any part of the coast of one Party which, because of its geographic situation, cannot overlap
with the extension of the coast of the other, is to be excluded from further consideration by
the Court. It is clear from the map that there comes a point on the coast of each of the two
Parties beyond which the coast in question no longer has a relationship with the coast of the
other Party relevant for submarine delimitation. The sea-bed areas off the coast beyond that
point cannot therefore constitute an area of overlap of the extensions of the territories of the
two Parties, and are therefore not relevant to the delimitation. In the view of the Court, in the
present context that point on the Tunisian coast is Ras Kaboudia ; on the Libyan coast it is
Ras Tajoura. The Court cannot, therefore, take into consideration such parts of the sea-bed of
the Pelagian Block as lie beyond those points. As for the boundaries to seaward of the area
145
relevant for the delimitation, these are not at present material and will be considered only in
relation to the criterion of proportionality, for the purposes of which such boundaries will
have to be defined. The conclusion that these areas are not legally relevant to the delimitation
between the Parties does not however lead to the conclusion by way of corollary that the
whole area bounded by the coasts of both countries and by such seaward boundaries is
reserved in its entirety for division between Libya and Tunisia. As mentioned above, the
rights of other States bordering on the Pelagian Sea which may be claimed in the northern and
north-eastern parts of that area must not be prejudged by the decision in the present case.
81. The “relevant circumstances which characterize the area” are not limited to the facts
of geography or geomorphology, either as a matter of interpretation of the Special Agreement
or in application of the equitable principle requiring all relevant circumstances to be taken
into account. Apart from the circumstance of the existence and interests of other States in the
area, and the existing or potential delimitations between each of the Parties and such States,
there is also the position of the land frontier, or more precisely the position of its intersection
with the coastline, to be taken into account. In that connection, the Court must in the present
case consider a number of alleged maritime limits resulting from the conduct of the States
concerned. It has further to give due consideration to the historic rights claimed by Tunisia,
and to a number of economic considerations which one or the other Party has urged as
relevant.
82. The absence of maritime boundaries formally agreed upon between the Parties
constitutes one of the difficulties of the present case, since the delimitation of the continental
shelf should start from the outer limit of the territorial sea, in accordance with a principle of
international law embodied in Article 1 of the 1958 Geneva Convention on the Continental
Shelf and Article 76, paragraph 1, of the draft convention on the Law of the Sea. Since there
has never been any agreement between Tunisia and Libya on delimitation of the territorial
sea, contiguous zones, exclusive economic zones, or the continental shelf, the undisputed land
frontier between the Parties established by a convention becomes a circumstance of
considerable relevance.
107. The Court is, however, of the view that these economic considerations cannot be
taken into account for the delimitation of the continental shelf areas appertaining to each
Party. They are virtually extraneous factors since they are variables which unpredictable
national fortune or calamity, as the case may be, might at any time cause to tilt the scale one
way or the other. A country might be poor today and become rich tomorrow as a result of an
event such as the discovery of a valuable economic resource. As to the presence of oil-wells
in an area to be delimited, it may, depending on the facts, be an element to be taken into
account in the process of weighing all relevant factors to achieve an equitable result.
133. A. The principles and rules of international law applicable for the delimitation, to be
effected by agreement in implementation of the present Judgment, of the areas of continental
shelf appertaining to the Republic of Tunisia and the Socialist People’s Libyan Arab
Jamahiriya respectively, in the area of the Pelagian Block in dispute between them as defined
in paragraph B, subparagraph (l), below, are as follows:
146
(1) the delimitation is to be effected in accordance with equitable principles, and taking
account of all relevant circumstances ;
(2) the area relevant for the delimitation constitutes a single continental shelf as the
natural prolongation of the land territory of both Parties, so that in the present case, no
criterion for delimitation of shelf areas can be derived from the principle of natural
prolongation as such ;
(3) in the particular geographical circumstances of the present case, the physical structure
of the continental shelf areas is not such as to determine an equitable line of delimitation.
