Continental Shelf (Tunisia / Libyan Arab Jamahiriya) (1982)

It is the case that tells you what equitable principles actually mean, thirteen years after North Sea announced them. It also separates the legal concept of the continental shelf from the physical one, and it identifies the relevant area as the first and most essential step in any delimitation.

Tunisia and Libya, adjacent States on the Gulf of Gabes, referred their continental shelf delimitation to the Court by Special Agreement. The Agreement asked the Court to take account of equitable principles, the relevant circumstances which characterise the area, and the new accepted trends in the Third Conference on the Law of the Sea. Both parties took the 1969 North Sea judgment as their starting point, and both treated natural prolongation as commanding; they differed on what natural prolongation meant and on how far considerations other than geography, geomorphology and geology could operate.

1. What are the applicable principles and rules, and what does equitable principles mean?
2. Is the legal continental shelf the same as the geographer's continental shelf?
3. How is the relevant area identified?

Delimitation is to be effected by agreement in accordance with equitable principles and taking account of all the relevant circumstances. Equity here is a legal concept applied as law, not a discretion. The legal concept of the shelf, though derived from a natural phenomenon, has pursued its own development and is wider than the physical one.

The starting point. Both parties accepted the North Sea formula, that delimitation is 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 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".

But the formula does not decide cases by itself. The Court's candid observation is worth quoting in an essay: the case "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." A formula that both parties accept can still produce opposite answers. That is why the meaning of equity matters.

Equitable principles cannot be defined in the abstract. This is the central passage. A principle is not equitable in itself; "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." The term equitable principles, the Court continued, "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."

The Court recalled its own words from 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". The problem is never whether to be equitable; it is how.

What equity is, as a legal concept. "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 municipal systems equity was often contrasted with the rigidity of positive law; in international law "this contrast has no parallel in the development of international law; the legal concept of equity is a general principle directly applicable as law." When applying positive international law, a court may choose among possible interpretations the one closest to the requirements of justice.

Equity distinguished from ex aequo et bono. "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." Here the Court's task was 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." And the disclaimer that keeps this within law: "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."

The legal shelf is not the geographer's shelf. Both parties agreed that the continental shelf is an institution of international law which, while remaining linked to a physical fact, is not to be identified with what the same term denotes in other disciplines. The Court traced the widening: at a very early stage the concept 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". The widening is most evident in the criterion of exploitability in Article 1 of the 1958 Convention, which defined the shelf by reference 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". That criterion 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."

Relevant circumstances and the relevant area. What is reasonable and equitable in any given case must depend on its particular circumstances, and "it is virtually impossible to achieve an equitable solution in any delimitation without taking into account the particular relevant circumstances of the area." The first and most essential step is to determine with greater precision what is the area in dispute and what is the area relevant to the delimitation.

Title comes from the coast. "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." The Court recalled from 1969 that the continental shelf is a legal concept in which the principle is applied that the land dominates the sea, and from the Aegean Sea case 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."

The consequence is practical: the coast of each party is the starting line, and only the areas lying off the Tunisian or the Libyan coast can be relevant to the claims.

• On equity, give the three propositions in order: equity is a direct emanation of the idea of justice; it is a general principle directly applicable as law; and it is distinct from a decision ex aequo et bono, which needs the parties' agreement under Article 38(2).
• The sentence that wins marks is that equitable principles cannot be interpreted in the abstract and refer back to whatever principles will achieve an equitable result. Equity in delimitation is result-oriented, not rule-oriented.
• On the concept of the shelf, the examinable contrast is between the 1958 exploitability criterion, which was open-ended, and Article 76 of the 1982 Convention, which fixed the outer limits by natural prolongation to the outer edge of the continental margin or 200 nautical miles, with the technical formulae in paragraph 4.
• Read this case immediately after North Sea. The first announced the standard; the second explained it. Then read Articles 74 and 83 of the 1982 Convention, which enact it.