rules for acquisition of territory

a. The rules for acquisition of territory were concisely summarized by the tribunal in the
first (1998) Eritrea/Yemen Arbitration Award:
“The modern international law of the acquisition (or attribution) of territory generally requires that there be: an intentional display of power and authority over the territory, by the exercise of jurisdiction and state functions, on a continuous and peaceful basis. The latter two criteria are tempered to suit the nature of the territory and size of its population, if any.”2
In the 1931 award in the dispute between Mexico and France over the sovereignty of Clipperton Island, located in the Pacific Ocean 1280 km (about 690 nautical miles) southwest of Acapulco, Mexico, the King of Italy as sole arbitrator had previously stated the rules this way:

It is beyond doubt that by immemorial usage having the force of law, besides the animus occupandi, the actual, and not the nominal, taking of possession is a necessary condition of occupation. This taking of possession consists in the act, or series of acts, by which the occupying state reduces to its possession the territory in question and takes steps to exercise exclusive authority there. Strictly speaking, and in ordinary cases, that only takes place when the state establishes in the territory itself an organization capable of making its laws respected. But this step is, properly speaking, but a means of procedure to the taking of possession, and, therefore, is not identical with the latter. There may also be cases where it is unnecessary to have recourse to this method. Thus, if a territory, by virtue of the fact that it was completely uninhabited, is, from the first moment when the occupying state makes its appearance there, at the absolute and undisputed disposition of that state, from that moment the taking of possession must be considered as accomplished, and the occupation is thereby completed.
****
1 See Ian Brownlie, PRINCIPLES OF PUBLIC INTERNATIONAL LAW, “The Creation and Transfer of Territorial
Sovereignty,” chapter 7 (7th ed. Oxford 2008).
2 Award of the Arbitral Tribunal in the first stage of the proceedings between Eritrea and Yemen (Territorial
Sovereignty and Scope of the Dispute, (1998) 22 RIAA, p. 268, para. 239). Judge Dugard, in his dissenting opinion
in the Pedra Branca/Pulau Batu Puteh case, stated:
This formulation requires serious attention for two reasons. First, because it gives effect to the
jurisprudence of contemporary international law from the time of Max Huber’s seminal decision in the
Island of Palmas Case (Netherlands/United States of America) (Award of 4 April 1928, RIAA, Vol. II
(1949), pp. 839, 868). Secondly, because it was expounded by a Tribunal comprising two former Presidents
of the International Court of Justice (Professor Sir Robert Y. Jennings and Judge Stephen M. Schwebel),
the President of the Court (Judge Rosalyn Higgins) and two highly experienced and well regarded
international law practitioners (Dr. Ahmed Sadek El-Kosheri and Mr. Keith Highet). In my view, this is a
formulation of the law on the acquisition of territory that is to govern all acquisitions of territorial title
based on the effective control of territory over a long period of time, including prescription, estoppel,
abandonment of title by the previous sovereign, acquiescence and tacit agreement evidenced by conduct.
(pages 150-151, para. 42).
2
There is no reason to suppose that France has subsequently lost her right by derelictio, since she never had the animus of abandoning the island, and the fact that she has not exercised her authority there in a positive manner does not imply the forfeiture of an acquisition already definitively perfected.3
In the separate opinion of Judge Carneiro in the case of the Minquiers and Ecrehos islands (France/United Kingdom), ICJ 1953, the judge laid out the rules for determining sovereignty in greater detail:
2. Criterion for the decision. -- In this Opinion I have confined myself to the following rules which were laid down by the Permanent Court of International Justice in the case concerning the Legal Status of Eastern Greenland:4
(a) the elements necessary to establish a valid title to sovereignty are “the intention and will to exercise such sovereignty and the manifestation of State activity” (pp. 46 and 63);
(b) in many cases international jurisprudence “has been satisfied with very little in the way of the actual exercise of sovereign rights, provided that the other State could not make out a superior claim. This is particularly true in the case of claims to sovereignty over areas in thinly populated or unsettled countries”. (p. 46);
(c) it is the criterion of the Court in each individual case which decides whether sovereign rights have been displayed and exercised “to an extent sufficient to constitute a valid title to sovereignty” (pp. 63-64).5
In this case, Judge Carneiro then applied these rules to the interpretation of treaties and other ancient documents by considering the following factors: the historical moment that the documents were concluded and their specificity regarding the islands in question; the attitudes of the parties regarding the features in question; geographical data; the natural unity of the islands; proximity of the mainland and relevant historical facts; acts of occupation; visits of fishermen; maps (which in this case were not taken into consideration); and diplomatic protests of the parties.
In cases where resolution of a dispute depends on legally significant facts that occurred, or a treaty concluded, centuries ago, the doctrine of inter-temporal law has become well-established: “in such cases the situation in question must be appraised, and the treaty interpreted, in the light of the rules of international law as they existed at that time, and not as they exist today.”6