The workload of the International Court of Justice in recent years has increasingly featured cases of disputes classified either as ‘territorial disputes’ or as ‘boundary disputes’, or otherwise involving the Court in considerations of the law relating to acquisition or transmission of territory, or to the creation, location and effect of territorial frontiers. The present survey analyzes the contributions to international law of the Court's decisions in these recent cases. Matters examined include the significance of the terms ‘boundary dispute’ or ‘territorial dispute’; the definition of what constitutes sovereign territory; titles and effectivités as bases for territorial claims; decolonization and the uti possidetis juris; use of natural features or of straight lines as boundaries; and relations across a frontier once established.
1 See, for example, Munkman, A.L.W., ‘Adjudication and Adjustment – International Judicial Decision and the Settlement of Territorial and Boundary Disputes’, (1972–1973) 46 BYIL 1, at 113; Thirlway, The Law and Procedure of the International Court of Justice (2013), Vol. I, at 543–76 and Vol. II, at 1431–90; Huh, S., ‘Title to Territory in the Post-Colonial Era: Original Title and Terra Nullius in the ICJ Judgments on Cases concerning Ligitan/Sipadan (2002) and Pedra Blanca (2008), (2013) 26 EJIL 709–25. On compliance with decisions of this kind, see the table at www.paulhensel.org/comply.html. Generally, on territorial boundaries: McCorquodale, R. and Pangalangan, R., ‘Pushing Back the Limitations of Territorial Boundaries’, (2001) 12 EJIL 867–88; Miller, D., ‘Boundaries, Democracy and Territory’, (2016) 61 American Journal of Jurisprudence 33–49.
2 See, for example, the citation from Mohammed Moray Abdullah, The United Arab Emirates: A Modern Hisory (1978), in the Separate Opinion of Judge Kooijmans in the case concerning Maritime Delimitation and Territorial Questions Between Qatar and Bahrain (Qatar v. Bahrain), Merits, Judgment of 16 March 2001,  ICJ Rep. 40, at 226–7, para. 5; and note the suggestion in Pedra Blanca/Pulau Batu Puteh of the existence of a ‘traditional Malay concept of sovereignty’, ‘based mainly on control over people, and not control over territory’, Sovereignty Over Pedra Branca/Pulau Batu Puteh, Middle Rocks and South Ledge (Malaysia/Singapore), Judgment of 23 May 2008,  ICJ Rep. 12, at 39, para. 76.
3 There have also been suggestions that even a definite boundary inherited from a colonial past may be open to challenge as being, as it were, ‘tainted’ by the manner of its creation. See for example McCorquodale and Pangalangan, supra note 1. The only case in which the ICJ may have recognized such a concept was the advisory case of Western Sahara, where it declined to accept that the relevant territory had been res nullius at the time of occupation, Western Sahara, Advisory Opinion of 16 October 1975,  ICJ Rep. 12, at 26, para. 39.
4 Maritime Delimitation and Territorial Questions Between Qatar and Bahrain (Qatar v. Bahrain), Merits, Judgment of 16 March 2001,  ICJ Rep. 40, at 97, para. 185; and as the Court recalled in the Black Sea case, ‘the land dominates the sea through the projection of the coasts or the coastal fronts’, Maritime Delimitation in the Black Sea (Romania v. Ukraine), Judgment of 3 February 2009,  ICJ Rep. 61, at 89, para. 77. For the territorial sea, it has long been ‘the low-water line along the coast’ that is adopted as ‘the normal baseline’ (1958 Convention on the Territorial Sea and the Contiguous Zone, 516 UNTS 205, Art. 3, repeated in 1982 United Nations Convention on the Law of the Sea, 1833 UNTS 3 (UNCLOS), Art. 5; and for claims to the continental shelf, EEZ etc., also it is this baseline that supplies the reference.
5 A judicial settlement may have more value as precedent than an agreed settlement, but only to the extent that it is based on considerations of general law, as distinct from the features peculiar to that case.
6 As recalled in the well-known dictum of the PCIJ in Case of the Free Zones of Upper Savoy and The District of Gex, Order of 19 August 1929, PCIJ Series A, No.22 (1929), 13.
7 Frontier Dispute (Burkina Faso/Niger), Judgment of 16 April 2013,  ICJ Rep. 44, at 66, para. 37. Niger opposed this request, and the Court rejected it on the basis of impeccable, if somewhat lengthy, arguments on the limits on the Court's jurisdiction, ibid., at 68–73, paras. 41–59.
8 The list of cases thus includes: 2015: Construction of a Road in Costa Rica along the San Juan River (Nicaragua v. Costa Rica); 2014: Maritime Dispute (Peru v. Chile); 2013: Aerial Herbicide Spraying (Ecuador v. Colombia); Frontier Dispute (Burkina Faso/Niger); 2012: Territorial and Maritime Dispute (Nicaragua v. Colombia); 2010: Pulp Mills on the River Uruguay (Argentina v. Uruguay); 2009 : Dispute regarding Navigational and Related Rights (Costa Rica v. Nicaragua); Maritime Delimitation in the Black Sea (Romania v. Ukraine); 2008: Sovereignty over Pedra Branca/Pulau Batu Puteh, Middle Rocks and South Ledge (Malaysia/Singapore); 2007: Territorial and Maritime Dispute between Nicaragua and Honduras in the Caribbean Sea (Nicaragua v. Honduras); 2005: Frontier Dispute (Benin/Niger); 2002: Sovereignty over Pulau Ligitan and Pulau Sipadan (Indonesia/Malaysia); Land and Maritime Boundary between Cameroon and Nigeria (Cameroon v. Nigeria: Equatorial Guinea intervening); 2001: Maritime Delimitation and Territorial Questions between Qatar and Bahrain (Qatar v. Bahrain); 1999: Kasikili/Sedudu Island.
9 Certain Activities carried out by Nicaragua in the Border Area (Costa Rica v. Nicaragua); Obligation to Negotiate Access to the Pacific Ocean (Bolivia v. Chile); Alleged Violations of Sovereign Rights and Maritime Spaces in the Caribbean Sea (Nicaragua v. Colombia); Maritime Delimitation in the Caribbean Sea and the Pacific Ocean (Costa Rica v. Nicaragua); Maritime Delimitation in the Indian Ocean (Somalia v. Kenya); Dispute over the Status and Use of the Waters of the Silala (Chile v. Bolivia); Land Boundary in the Northern Part of Isla Portillos (Costa Rica v. Nicaragua); Application for revision of the Judgment of 23 May 2008 in the case concerning Sovereignty over Pedra Branca/Pulau Batu Puteh, Middle Rocks and South Ledge (Malaysia/Singapore) (Malaysia v. Singapore); and the Request for Interpretation of the Judgment of 23 May 2008 in the case concerning Sovereignty over Pedra Branca/Pulau Batu Puteh, Middle Rocks and South Ledge (Malaysia/Singapore) (Malaysia v. Singapore).
10 Maritime Delimitation in the Black Sea (Romania v. Ukraine), supra note 4, at 85, para. 64.
11 In respect of the ‘distinctly modern legal concepts’ of the EEZ and continental shelf, it has been suggested that it is anachronistic to invoke the uti possidetis juris: Nicaragua in Territorial and Maritime Dispute between Nicaragua and Honduras in the Caribbean Sea (Nicaragua v. Honduras), Judgment of 8 October 2007,  ICJ Rep. 659, at 728, para. 231. In Maritime Delimitation in the Black Sea it was contended that ‘[a]s a matter of legal principle, effectivités or “State activities” cannot constitute an element to be taken into account for the purposes of maritime delimitation’, supra note 4, at 124, para. 193. The Court's response was more guarded: ibid., at 125, paras. 197–8.
12 Frontier Dispute (Burkina Faso/Republic of Mali), Judgment of 22 December 1986,  ICJ Rep. 554, at 563, para. 17.
14 Frontier Disputes have included Burkina Faso/Mali (1986); Benin/Niger (2005); Burkina Faso/Niger (2013), and the Land, Island and Maritime Frontier Dispute, El Salvador v. Honduras (1992). Territorial Disputes include Libya/Chad (1994) and (with the addition of ‘and Maritime’) Nicaragua v. Honduras (2007) and Nicaragua v. Colombia (2012). Other disputes of the same kind have been given other titles, e.g., referring to the geographical or other feature disputes (e.g., Temple of Preah Vihear).
15 Territorial Dispute (Libyan Arab Jamahiriya/Chad), Judgment of 3 February 1994,  ICJ Rep. 6, at 14, para. 19.
17 Ibid., 14–15, paras. 18–21.
18 Ibid., 38, para. 75.
19 Conceivably equity could be invoked: cf. the Court's division of the Pool of Soum in the Frontier Dispute (Burkina Faso/Mali) case: below, text and fn. 71.
21 Cf. the handling by the Court of the ‘unclaimed area’ in the Burkina Faso/Niger case: below, text and fn. 72.
22 Sovereignty over Pulau Ligitan and Pulau Sipadan (Indonesia/Malaysia), Judgment of 17 December 2002,  ICJ Rep. 625, at 648, para. 43.
23 This term has been in use in relation to the question whether a dispute is within the Court's jurisdiction, or admissible; but it does not seem that significance of the term is identical in that and in the present context.
24 See for example H. Thirlway, The International Court of Justice (2016), 53–5.
25 Actions relevant for this purpose are referred to as effectivités, and discussed in Section 6 below.
26 Territorial and Maritime Dispute (Nicaragua v. Colombia), Merits, Judgment of 19 November 2012,  ICJ Rep. 624, at 652.
28 Sovereignty over Pulau Ligitan and Pulau Sipadan (Indonesia/Malaysia), supra note 22, at 682, para. 135. The Court also noted a circumstance to be taken into account was ‘the extent to which sovereignty is also claimed by some other Power’.
29 It has been judicially noted that a relevant consideration in relation to a territorial claim is ‘the extent to which sovereignty is claimed by some other power’ (see text and fn 114 below), but the PCIJ, at least, meant simply that the Court must examine that other claim, not that its existence affected the assessment of the actions of the claimant before it.
30 Supra note 22, at 28, para. 33. The terms of that opposition excluded the remaining disputed features (Middle Rocks and South Ledge); crystallization of claims to these occurred with a formal assertion of sovereignty in 1993; ibid., paras. 35–6.
31 Territorial and Maritime Dispute (Nicaragua v. Colombia), supra note 26, at 653, para. 71.
32 Frontier Dispute (Benin/Niger), Judgment of 12 July 2005,  ICJ Rep. 90, at 143, para. 127.
33 Ibid. (Judge Bennouna, Dissenting Opinion), at 154, para. 9.
34 In the Oil Platforms case it was argued that Iran's oil platforms could not be said, for the purposes of a treaty provision, to be on the ‘territory’ of Iran, ‘inasmuch as they are outside Iran's territorial sea, though upon its continental shelf and in its exclusive economic zone’, Oil Platforms (Islamic Republic of Iran v. United States of America), Judgment of 6 November 2003,  ICJ Rep. 161, at 200, para. 82. The Court did not find it necessary to resolve the point.
35 An unusual situation arose in the Maritime Dispute (Peru v. Chile): despite its name, this case also involved a small extent of land boundary, as the parties disagreed as to the endpoint of the territorial boundary and the starting point of the maritime boundary. It became apparent that these two points were not necessarily identical. Since it is the coast that generates the seabed rights, normally the starting point of the maritime boundary would necessarily be the endpoint of the land boundary; but a boundary is essentially a creature of agreement; the parties were thus free to fix two separate points, though in the case in question they had probably done so unwittingly. At all events, the Court, being seised of (and having jurisdiction over) a maritime boundary dispute, confined itself to declaring the location of the starting point of the maritime boundary, leaving the situation on land undefined: ‘The Court is not called upon to take a position as to the location of Point Concordia, where the land frontier between the Parties starts. It notes that it could be possible for the aforementioned point not to coincide with the starting-point of the maritime boundary, as it was just defined. The Court observes, however, that such a situation would be the consequence of the agreements reached between the Parties.’ Maritime Dispute (Peru v. Chile), Judgment of 27 January 2014,  ICJ Rep. 3, at 64, para. 175.
36 In Territorial and Maritime Dispute (Nicaragua v. Colombia), the Court mentioned the far-reaching effects of declaring a particular feature an island as a reason for requiring good evidence to support the conclusion, see Territorial and Maritime Dispute (Nicaragua v. Colombia), supra note 26, at 644, para. 36.
37 In Territorial and Maritime Dispute (Nicaragua v. Colombia), Nicaragua argued that ‘naturally formed’ excluded a feature wholly composed of coral debris, but the Court ruled that geological composition was irrelevant, ibid., supra note 26, at 635, para. 37. Art. 13 of UNCLOS gives, in connection with the territorial sea, a definition of ‘low-tide elevations’.
38 In Pulau Ligitan and Pulau Sipadan, Judge Oda suggested that the ‘equitable’ allotment of seabed areas should limit the effect given to ‘tiny islands’, supra note 22, at 690 (Judge Oda, Declaration); but in the Territorial and Maritime Dispute (Nicaragua v. Colombia) the Court confirmed earlier findings that ‘even the smallest island generates a 12-nautical-mile territorial sea’, see supra note 26, at 644, para. 36.
41 Special Agreement, Article 2, see supra note 22, at 630.
42 See supra note 22, at 634, para. 14.
43 Supra note 2, at 22, paras. 16–19.
44 Ibid., at 96–9, paras. 278, 290.
45 Ibid., para. 291.
46 But which of them the Court did not decide, ibid., 101, paras. 297–9. Note, however, that on 30 June 2017 Malaysia filed a Request for Interpretation of the 2008 Judgment, indicating that the Parties have been unable to agree on the meaning and/or scope of the Court's finding concerning South Ledge.
47 Supra note 26, at 641, para. 25.
48 Ibid., para. 26.
49 Ibid., at 645, para. 37; and see also at 642–3, paras. 30–1.
50 In Land and Maritime Boundary between Cameroon and Nigeria, the Court mentioned the existence of ‘the established modes of acquisition of title in international law’, but did not enumerate them, Land and Maritime Boundary Between Cameroon and Nigeria (Cameroon v. Nigeria: Equatorial Guinea intervening), Merits, Judgment of 10 October 2002,  ICJ Rep. 303, at 352, para. 65.
51 See for example M. Kohen and M. Hébié, ‘Territory, Acquisition’, Max Planck Encyclopedia of International Law 1118, para. 7. It has also been suggested that title may be acquired through international adjudication: see Post, H., ‘Adjudication as a mode of acquisition of territory? Some observations on the Iraq/Kuwait boundary arbitration in the light of the jurisprudence of the International Court of Justice’, in Lowe, V. and Fitzmaurice, M. (eds.), Fifty Years of the International Court of Justice (1996), 237 . The Roman institution of adjudicatio might be suggested as a parallel, but this is either limited to a judgment dividing a jointly held property, or simply the effective part of a decision awarding a disputed property, not the reason for the award. See Sohm, The Institutes of Roman Law (1892), 236–7.
52 Cf. Certain Frontier Land [the problem dated back to the separation of Belgium and the Netherlands in 1839, and was resolved by Court 120 years later], Judgment of 20 June 1959; Sovereignty over Certain Frontier Land (Belgium/Netherlands), Judgment of 20 June 1959,  ICJ Rep. 209. In Pedra Branca/Pulau Batu Puleh Malaysia invoked the concept of ‘possession immemorial’ – ‘that which has lasted for such a long time that it is impossible to provide evidence of a different situation and of which anybody recalls having heard talk’ (quoted from the 1902 Meerauge arbitration): supra note 2, at 32, para. 48; the Court found it unnecessary to consider this suggestion.
53 See supra note 11, at 704, para. 145; see also ibid., at 743. para. 280, for similar reasons rejecting the island as a base-point for constructing a maritime boundary.
54 In Sovereignty over Pedra Branca/Pulau Batu Puteh, Middle Rocks and South Ledge, the Court indicated that ‘Any passing of sovereignty might be by way of agreement between the two States in question. Such an agreement might take the form of a treaty . . . The agreement might instead be tacit and arise from the conduct of the Parties. International law does not, in this matter, impose any particular form. Rather it places its emphasis on the parties’ intentions’: supra note 2, at 50, para. 120, citing Temple of Preah Vihear (Cambodia v. Thailand), Case Concerning the Temple of Preah Vihear (Cambodia v. Thailand), Preliminary Objections, Judgment of 26 May 1961,  ICJ Rep. 17, at 31.
55 Gabčíkovo-Nagymaros Project (Hungary/Slovakia), Judgments of 25 September 1997,  ICJ Rep. 7, at 23; and note the mention of this by Judge Bedjaoui as relevant to the nature of the treaty as a territorial treaty, ibid., at 125, paras. 21, 22 (Judge Bedjaoui, Separate Opinion).
56 For the distinction between cession and occupation of terra nullius (see below), see the advisory opinion in Western Sahara, supra note 3, at 39, para. 80. For the effect of treaties of ‘protection’ concluded with indigenous local rulers, see Land and Maritime Boundary between Cameroon and Nigeria, supra note 50, at 404–5, paras. 204–5.
57 See supra note 2, at 50, para. 121. In the Land, Island and Maritime Frontier Dispute, the Chamber held that a protest by Honduras in 1991, coming after a long history of acts of sovereignty by El Salvador in Meanguera, was made too late to affect the presumption of acquiescence on the part of Honduras. ‘The conduct of Honduras vis-à-vis earlier effectivités reveals an admission, recognition, acquiescence or other form of tacit consent to the situation’, Land, Island and Maritime Dispute (El Salvador/Honduras: Nicaragua intervening), Merits, Judgment of 11 September 1992,  ICJ Rep. 351, at 577, para. 364.
58 Supra note 2, at 96, para. 276.
59 In the Pedra Blanca case, the transaction was seen by the UK, the receiving party, as a cession, but the other party was not informed that that was the UK's interpretation, and this for the Court meant that it did not qualify as such: supra note 2, at 56, para. 136.
60 Which, for our purposes, may include secession (cf. J. Crawford, The Creation of States in International Law (2007), Ch. 9). Succession is defined as ‘the replacement of one State by another in the responsibility for the international relations of territory’ (Vienna Convention on Succession of States in Respect of State Property, Archives and Debts, Art. 2(1)(b); Vienna Convention on Succession of States in Respect of Treaties, Art. 2(a)). It is in these contexts that the concept is of greater relevance than in relation to title. On the significance of succession as ‘a recognition by the State of certain legal consequences flowing from [specified] circumstances’ rather than an act of will, see Application of the Convention on the Prevention and Punishment of the Crime of Genocide (Croatia v. Serbia), Preliminary Objections, Judgment of 18 November 2008,  ICJ Rep. 412, at 450, para. 109.
61 Frontier Dispute (Benin/Niger), supra note 32, at 120, para. 45.
62 Supra note 22, at 669–78, paras. 94–124.
63 Ibid., at 678, para. 124.
64 ‘Conquest only operates as a cause of loss of sovereignty when there is war between two States and by reason of the defeat of one of them sovereignty over territory passes from the loser to the victorious State’, Legal Status of Eastern Greenland, Judgment of 5 April 1933,  PCIJ Series A/B, No.53, at 47. See, e.g., Oppenheim, International Law (1948), 241a. The recognition of title by conquest was, prior to the Covenant of the League, the Charter of the United Nations, and the General Treaty for the Renunciation of War, the necessary result of the admissibility of the right of war as an instrument both for enforcing the law and for changing existing rights. As in the case of colonization, the intertemporal principle requires nevertheless that effect be given to such processes if they were valid at the time that they occurred.
65 Legal Consequences of the Construction of a Wall in the Occupied Palestinian Territory, Advisory Opinion of 9 July 2004,  ICJ Rep. 136, at 184, para. 121. For the suggestion that establishment by one African State of villages on the territory of its neighbour constituted ‘acts of conquest’ and thus not creating a valid title, see Land and Maritime Boundary between Cameroon and Nigeria, supra note 50, at 451, para. 63.
66 For the limits of military occupation, see Art. 42 of the 1907 Hague Regulations, and Palestine Wall, supra note 65, at 167, para. 76.
67 Terra nullius being, it has been said, a ‘discredited concept . . . of no contemporary application’, Palestine Wall case, supra note 65, at 237, para. 8 (Judge Al-Khasawneh, Separate Opinion).
68 Cf. Right of Passage over Indian Territory (Portugal v. India), Judgment of 12 April 1960,  ICJ Rep. 6, at 37.
69 Cf. Legal Status of Eastern Greenland, P.C.I.J., Series A/B, No. 53, 44 f. and 63 f.
70 Western Sahara, supra note 3, at 39, para. 79. The territory might nonetheless be inhabited, and yet nullius, if the inhabitants could be shown to lack ‘social and political organization’, ibid., para. 80.
71 In Frontier Dispute (Burkina Faso/Mali), the Chamber was faced with a similar difficulty inasmuch as there was no way of determining whether the frontier line passed on one side of a particular feature (the Pool of Soum), or the other side, or ran through it, and in the latter case, how it divided the Pool: the Court drew a line which divided the Pool in an equitable manner, see supra note 12, at 633, paras. 149–50.
72 Supra note 7, at 78, para. 74. Roman law recognized title by adjudicatio: some echo of that concept may be seen here.
73 If neither party had sovereignty, there would be an area in which there was no frontier between the parties, but two parallel frontiers between each and the ‘missing’ area; and in casu the terms of the Special Agreement excluded this. This is probably what the Court had in mind in the passage quoted.
74 Award of the Arbitral Tribunal in the first stage of the proceedings between Eritrea and Yemen (Territorial Sovereignty and Scope of the Dispute), Decision of 9 October 1998, UNRIAA Vol XXII, at 239, para. 106; at 253, paras. 164–5.
75 Or perhaps, known to any other potential claimant or title-holder: cf. Kasikili/Sedudu Island (Botswana/Namibia), Judgment of 13 December 1999,  ICJ Rep. 1045, at 1103, para. 94.
76 Ibid. A similar enumeration is given by Judges Abraham and Simma in the Joint Dissenting Opinion in Pedra Branca: supra note 2, at 122, para. 17 (Judges Abraham and Simma, Joint Dissenting Opinion).
77 Supra note 75, at 1105, para. 97.
78 Note also the distinction between the common law system (prescription limited to establishment of rights over another's land, but acquisition by squatting seen as a matter of limitation of actions) and continental systems (where prescription (Ersitzung, préscription) can establish title). It was the French and German judges in Pedra Blanca who dissented on ground that the decision should have been based on prescription, which in their view was the application of the idea of consent/acquiescence in this specialized field.
79 According to Judge ad hoc Dugard, ‘the Court studiously avoided any suggestion that its Judgment was based on prescription’: supra note 2, at 146, para. 33 (Judge ad hoc Dugard, Dissenting Opinion).
80 Joint Dissenting Opinion, supra note 75, at 119–20, para. 11.
81 Dissenting Opinion, supra note 78, at 146, para. 33.
82 See supra note 2, at 96, paras. 276–7. It was argued by Judges Simma and Abraham that the Court had failed to make clear whether it was relying on tacit agreement or acquiescence: see their Joint Dissenting Opinion, supra note 78, at 118–22 (Section III).
83 The expression seems to have been taken from the Court's judgment in the Fisheries case ( ICJ Rep. 116, at 138, quoted at 352, para. 65, supra note 50). For the Court's summary of the Nigerian contention, see supra note 50, at 349, para. 62.
84 Supra note 50, at 352, para. 65.
85 See ibid., at 476, para. 8; at 581–3, paras. 134–7 (Judge Koroma, Dissenting Opinion/ Judge ad hoc Ajibola, Dissenting Opinion, respectively).
86 In the case of long-established states with stable boundaries, the concept of title may be taken to cover the territory that has long been that of the state, any enquiry into the precise means of acquisition perhaps centuries ago being supererogatory (and possibly tactless, since such means may include conquest or other methods no longer recognized as legitimate).
87 Supra note 12, at 582, para. 54; cited in Kasikili/Sedudu Island, supra note 75, at 1098, para. 84; Pulau Ligitan and Pulau Sipadan, supra note 22, 667, para. 88; Territorial and Maritime Dispute (Nicaragua v. Honduras), supra note 11, 723, para. 215. In the 1986 decision, the Court, however, also emphasized that a ‘legal title’ is not limited to ‘documentary evidence’; but ‘the concept of title may also, and more generally, comprehend both any evidence which may establish the existence of a right, and the actual source of that right’: see supra note 12, at 564, para. 18.
88 Maritime Delimitation and Territorial Questions between Qatar and Bahrain, supra note 4, at 68, para. 89.
89 Approved and incorporated in the 1931 Henderson-Fleuriau Exchange of Notes: supra note 50, at 335, para. 41, at 340, para. 50.
90 Frontier Dispute (Benin/Niger), supra note 32, at 126–7, paras. 71–4.
91 It may also be relied on simply as a piece of evidence, e.g., of the views of the parties at the time of its conclusion as to their territorial rights: see below, the end of this section.
92 Cf. Kasikili/Sedudu Island, supra note 74, at 1102, para. 93.
93 See supra note 26, at 649, para. 56 (emphasis added).
94 Ibid., at 732, para. 8 (Judge Abraham, Separate Opinion).
95 Supra note 15, at 22–3, para. 43.
96 Ibid, at 38, para. 75.
97 See supra note 7, at 148, para. 47 (Judge Yusuf, Separate Opinion). The importance of the matter, in this judge's view, was doubt as to the long-standing view that the situation in Africa on decolonization, and the measures adopted to deal with it, were the same as those that had existed in Latin America; in his view it was not the principle of uti possidetis iuris that had been adopted in Africa, but a different principle.
98 But, as pointed out by Judge Abraham in Nicaragua v. Colombia, the treaty has to be applied first: effectivités are to be used to interpret it, not to replace it.
99 See above, text and fn. 16 as to the importance of specific jurisdiction.
100 See supra note 22, at 678, paras. 125–6.
101 Supra note 4, at 68, paras. 87–9.
102 Ibid., para. 89: note that in this case it was the ‘understanding’, not of the parties to the dispute, but of third states with an interest in the region, thus representing a sort of international recognition of a legal situation.
105 Supra note 2, at 95, para. 271, also quoted in Certain Activities Carried Out by Nicaragua in the Border Area (Costa Rica v. Nicaragua) and Construction of a Road in Costa Rica along the San Juan River (Nicaragua v. Costa Rica), Merits, Judgment of 16 December 2015,  ICJ Rep. 665, at 703, para. 85. The Arbitral Tribunal also observed that map evidence ‘cannot be used as indicative of legal title’, but ‘is nevertheless important evidence of general opinion or repute’; paragraph 381 of the Award, quoted in the Joint Dissenting Opinion of Judges Bedjaoui, Bennouna and Koroma in Qatar v. Bahrain, supra note 4, at 190, para. 144 (Joint Dissenting Opinion of Judges Bedjaoui, Bennouna and Koroma).
107 Supra note 26, at 644, para. 35 (chart showing dangers to navigation not concerned with low-tide elevations).
108 Cf. the statement of the Guatemala/Honduras Special Boundary Arbitral Tribunal, cited in the Territorial and Maritime Dispute (Nicaragua v. Honduras), supra note 11, at 722–3, para. 213.
109 See supra note 7, at 76, para. 68.
110 Supra note 50, at 366–7, paras. 101–2.
111 Supra note 26, at 662, para. 102.
112 Supra note 11, at 712, para. 172.
113 Legal Status of Eastern Greenland, supra note 64, at 45–6.
115 Whether the pre-existing title has ceased to exist or has become transferred to the new sovereign is unclear; the distinction normally makes no practical difference.
116 See supra note 12, at 587, para. 63, quoted in part in Sovereignty over Pulau Ligitan and Pulau Sipadan, supra note 22, at 678, para. 126. The various hypotheses have here been numbered for convenience of reference.
117 Supra note 2, at 31, para. 45.
118 Ibid., at 31–7, paras. 46–69; this is not stated, but seems to be the implication of the Court's action.
119 Supra note 64, at 45–6, cited in the Nicaragua v. Honduras case, supra note 11, at 712, para. 173. The PCIJ case is one that appears not to fall into any of the categories enumerated in Burkina Faso/Mali, as neither claimant relied on a title; in Nicaragua v. Honduras the Court eventually resolved the dispute similarly on the basis of a choice between rival post-colonial effectivités: supra note 11, 711ff.
120 Supra note 50, at 353, para. 67. Similarly in Pedra Blanca, Judges Simma and Abraham pointed out that the judge must be more exigent as to effectivités where there is a pre-existing title, because it is not so much the effectivités themselves, as such, that have to be assessed, but the presence or absence of acquiescence on the part of the title-holder: supra note 2, at 120, para. 13 (Judges Simma and Abraham, Joint Dissenting Opinion).
121 See supra note 50, at 353, para. 68.
122 Or ‘colonial effectivités’: see further in Section 7 below.
123 Supra note 32, at 127, para. 78.
124 Supra note 11, at 713–22, paras. 176–208.
125 Ibid., at 721, paras. 207–8.
126 Supra note 22, at 678, para. 127.
127 A point made by Judge Oda, who thought the case a ‘weak’ one, in his Declaration: ibid., at 687.
128 See supra note 32, at 148–9, para. 141,
129 See supra note 75, at 1105, para. 98: the Court did not there use the expression ‘effectivités’; it was also examining the issue on the basis of Namibia's claim of to a prescriptive title (ibid., at 1106, para. 99).
130 Cf. the dispute between Libya and Chad, mentioned in this context above, which Chad designated as a boundary dispute (on the basis that there existed a boundary) and Libya regarded as a territorial dispute, because no boundary yet existed: the Court gave the case the title Territorial Dispute (Libya/Chad), since that was the term used in the special agreement by which the Court was seised; but see the Court's discussion of the rival terms at 14–15, paras. 19–21, supra note 15. The case concerning the dispute between Benin and Niger was, however, entitled Frontier Dispute.
131 See supra note 57, at 408, para. 80.
132 Land and Maritime Boundary between Cameroon and Nigeria, supra note 50, at 353, para. 68, citing in support the Land, Island and Maritime Territory Dispute, supra note 57, at 408–9, para. 80. The reference to ‘treaty title’ may be misleading, as the only entities able to modify the effect of a treaty by subsequent agreement, express or tacit, are the parties, or their successors in title. If, for example, the titles of two states to two adjacent territories derive from two separate accessions to independence, those titles are not treaty-titles (or ‘conventional’ titles) in the sense that they derive from an agreement between the two states which the two states may amend. This is not to say that in such a case the boundary between them is unalterable, but it seems the theory of treaty amendment cannot be invoked to explain an alteration process.
133 Construction of a Road/Certain Activities, supra note 105, at 665, para. 89.
134 See supra note 7, at 79, para. 78.
135 Ibid., at 84, para. 98.
137 In this sense, Judges Simma and Abraham, Joint Dissenting Opinion, Pedra Branca, supra note 120, at 120, para. 13.
138 On the principle generally, see Shaw, M., ‘The Principle of Uti Possidetis Juris Today’, (1996) 67 BYBIL 9 ; H. Ghebrewebet, Identifying Units of Statehood and Determining International Boundaries: A Revised Look at the Doctrine of Uti Possidetis and the Principle of Self-Determination (2006).
139 Though in a different form in Brazil: see Barberis, J.A., ‘La conception brésilienne de “uti possidetis”’, in Yakpo, E. and Boumedra, T. (eds.), Liber Amicorum Mohammed Bedjaoui (1999), 49–62 .
140 In the Frontier Dispute (Burkina Faso/Mali) it found that the principle was ‘not a special rule which pertains solely to one specific system of international law’, but ‘a general principle, which is logically connected with the phenomenon of the obtaining of independence, wherever it occurs’, supra note 12, at 565, para. 20. On the other hand, the Chamber in the Frontier Dispute (Benin/Niger) used wording limited to its application in Africa, supra note 32, at 108, para. 23. For an earlier view, see E. Yakpo, ‘The African Concept of uti possidetis – Need for Change?’, in the Bedjaoui festschrift, supra note 140.
141 Supra note 4, at 73, para. 105.
142 Ibid., at 85, para. 148.
143 On the contrary, they are likely to agree that the disputed territory is not terra nullius, ‘on the basis of diametrically opposed reasoning, each of them claiming to hold title . . .’: Pulau Ligitan and Pulau Sipadan, supra note 22, at 674, para. 108.
144 A case in which it was also argued that uti possidetis juris applies to maritime rights, see supra note 11, at 727–9, paras. 228–36; this possibility will not be explored here.
145 Ibid., at 701, para. 134.
146 Ibid., at 706–7, para. 154.
147 Ibid., at 710, paras. 165–7.
148 As noted above, and stated in Frontier Dispute (Burkina Faso/Mali), supra note 12, at 587, para. 63.
149 Supra note 22, at 652–3, para. 52; at 665, para. 80; at 668, para. 92.
150 Ibid., at 669ff., para. 93ff.
151 Ibid., at 685–6, paras. 148–9.
152 Supra note 32, at 109, para. 25.
153 As Judge Kooijmans pointed out in Qatar/Bahrain, the principle does not apply to the boundary between two territories which were formerly colonies of different states, as such boundary is already international: supra note 2, at 231, para. 22. This was also the situation in Land and Maritime Boundary (Cameroon/Nigeria).
154 Frontier Dispute (Benin/Niger), supra note 32, at 148, para. 140. In the Frontier Dispute (Burkina Faso/Mali) the Court seems have tried to downgrade the role of colonial law (see supra note 12, at 568, para. 30); but this is more political window-dressing than international law. Compare foreign law as fact and as law in private international law.
155 See supra note 32, at 127–32.
157 Or, in the curious expression used in Pedra Blanca, showed ‘acquiescence in the abandonment of its title’, supra note 2, at 354, para. 70.
158 Land and Maritime Boundary (Cameroon/Nigeria), supra note 50, at 336, para. 44 (Cameroon's argument, impliedly upheld), ibid., 340, para. 49.
159 Supra note 7, at 79–80, para. 81. Straight lines were often used for colonial boundaries: Shaw indicates that some 30 per cent of pre-independence boundaries in Africa followed geometrical lines: M.A. Shaw, Title to Territory in Africa: Legal Issues (1986), 70.
160 Para. 22 (A).
161 Supra note 7, at 88, para. 105. It is also unclear how long the ‘small hut’ referred in the Award of General Alexander (one of the elements of title discussed in the Nicaragua v. Costa Rica case) continued to be available as a boundary-defining feature: see RIAA Vol XXVIII, p. 220, cited at 698, para. 73, supra note 105.
162 See Euclid, Elements, Bk. 1, Definition 2.
163 Supra note 74, at 1106, para. 101.
164 In Frontier Dispute (Benin/Niger), Judge Bennouna disagreed with the decision because he held that the relevant texts provided for a boundary on the left bank of the River Niger: see supra note 32, at 156, paras. 19 ff. (Judge ad hoc Bennouna, Dissenting Opinion).
165 Supra note 74, at 1061–2, para. 24.
166 See supra note 32, at 149, para. 144.
167 Supra note 7, at 85, para. 101. This was apparently an assessment of the presumed intention of the colonial legislator; the Court thus does not seem to have contemplated the possible existence of a right of one riparian state to draw water from a river that is under the sovereignty of the other, comparable to an easement or servitude. There seems no reason why such a right could not be created by agreement, or even long usage implying acquiescence. Cf. the relevance, in the Frontier Dispute (Burkina Faso/Mali), of access to a frontier pool for the watering of cattle: see supra note 12, at 632, para. 146.
168 See supra note 7, at 85, para. 101.
169 Dispute over the Status and Use of the Waters of the Silala (Chile v. Bolivia), Application of Chile, para. 3.
170 In the case of a tidal river, this may also raise questions of the choice of high- or low-water mark as boundary.
171 Supra note 32, at 141, para. 121.
172 Ibid., para. 126.
173 Note in this connection the study of E, Milano, ‘Territorial Disputes, Unlawful Territorial Situations and State Responsibility’, (2004) The Law and Practice of International Courts and Tribunals 509–41
175 The claim was based primarily on a treaty between the parties, but it was also asserted on the basis of alleged ‘rules of general international law’: Dispute regarding Navigational and Related Rights (Costa Rica v. Nicaragua), Judgment of 13 July 2009,  ICJ Rep. 213, at 232, para. 32.
176 Ibid., at 233, para. 34.
177 See supra note 105, at 718, paras. 137, 142. The Court, however, indicated that the Parties might request in the Court's assistance in determining the amount of compensation due, if negotiations should fail within 12 months after the Judgement. Costa Rica filed such a request on 16 January 2017 (see Order fixing time-limits, 2 February 2017).
178 Ibid., at 704, para. 97. Note, however, that in the preceding paragraphs dealing with the claim of breach of Costa Rica's territorial sovereignty there is no comparable reference to the presence or absence of Nicaragua's mens rea, but it would seem that this was regarded as unnecessary.
179 Corfu Channel, United Kingdom v. Albania, Merits, Judgment of 4 April 1949,  ICJ Rep. 4, at 22.
180 Pulp Mills on the River Uruguay (Argentina v. Uruguay), Judgment of 20 April 2010,  ICJ Rep. 14, at 55–6, para. 101, citing the Corfu Channel case, supra note 179, at 22.
181 Construction of a Road in Costa Rica along the San Juan River and Certain Activities carried out by Nicaragua in the Border Area, supra note 104, at 707–8, para. 106.
182 Aerial Herbicide Spraying, Ecuador's Application, para. 2. The case was later discontinued, on terms that suggested that Colombia recognized the validity of Ecuador's complaint: Aerial Herbicide Spraying (Ecuador v. Colombia), Order of 13 September 2013,  ICJ Rep. 278.
183 See supra note 180, at 42, para. 52.
184 In this sense R. Kolb, The International Court of Justice (2013), 1159, citing as early examples the Nauru and Gabćikovo cases: see the statement of principle in the latter case at 41, para. 53, supra note 55.
185 Supra note 81, at 83, para. 204; but note the discretion allowed to the state concerned in assessing the content of the assessment to be carried out, ‘having regard to the nature and magnitude of the proposed development and its likely adverse impact on the environment’: ibid., at 83, para. 205. Could a claim be based simply on a failure to carry out such an assessment, even if the planned activity had never been set on foot?
186 Certain Activities Carried out by Nicaragua in the Border Area/Construction of a Road in Costa Rica along the San Juan River, supra note 105, at 665, para. 104.
* Professor of International Law; formerly in the service of the ICJ, for many years as Principal Legal Secretary.
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