Challenging the Notion of a “Single Continental Shelf”

Abstract

According to international courts and tribunals, there exists in law only a “single continental shelf,” rather than an “inner” and an “outer” continental shelf. What originally started as a simple phrase to justify the jurisdiction of the court or tribunal eventually ended up as a justification for using the traditional delimitation methodology for delimitation of the continental shelf beyond 200 NM. This article challenges the notion of a “single continental shelf” on various bases, namely, with respect to bases of entitlement, delineation formulas, the nature of coastal state rights, and the inapplicability of the equidistance line beyond 200 NM.

Keywords:

• continental shelf
• delimitation
• delineation
• entitlement

Acknowledgments

This article builds upon a presentation given by the author at the annual conference of the Norwegian Centre for the Law of the Sea with the theme Ocean Space, held in Tromsø on 23–24 November 2022; see https://uit.no/tavla/artikkel/771558/nclos_conference_2022. The author acknowledges Tessie van der Voort Maarschalk for the artwork she created for this article.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Notes

1 Convention on the Continental Shelf, adopted 29 April 1958, entered into force 10 June 1964, 499 UNTS 311.

2 United Nations Convention on the Law of the Sea, adopted 10 December 1982, entered into force 16 November 1994, 1833 UNTS 397.

3 Final Act of the Third United Nations Conference on the Law of the Sea, A/CONF.62/121, Official Records of the Third United Nations Conference on the Law of the Sea, Volume XVII (Plenary Meetings, Summary Records and Verbatim Records, as well as Documents of the Conference, Resumed Eleventh Session and Final Part Eleventh Session and Conclusion) (1982), Annex II.

4 The first time this statement was made was in Maritime Delimitation (Barbados v. Trinidad and Tobago) (Award of the Arbitral Tribunal of 11 April 2006) XXVII RIAA 147, [213].

5 Despite the notion of a “single continental shelf” gaining traction in case law and scholarly literature, there are a few scholars who have raised doubt about this notion and/or its underlying presumptions. In this respect, this article builds upon what has been said before. See Leonardo Bernard, “The Problem with the Concept of ‘Single Continental Shelf’’” (2022) 7 Asia-Pacific Journal of Ocean Law and Policy 91; Malcolm Evans, “Maritime Boundary Delimitation: Whatever Next?” in Jill Barrett and Richard Barnes (eds), Law of the Sea: UNCLOS as a Living Treaty (British Institute of International and Comparative Law BIICL, 2016), 41, 74–75; Tara Davenport, “The China–Japan Dispute over Entitlement in the East China Sea: Legal Issues and Prospects for Resolution” in Clive H. Schofield, Seokwoo Lee and Moon-Sang Kwon (eds), The Limits of Maritime Jurisdiction (Brill Nijhoff, 2013), 297, 316–318; Bjorn Kunoy, “Admissibility of a Plea to an International Adjudicative Forum to Delimit the Outer Continental Shelf Prior to the Adoption of Final Recommendations by the Commission on the Limits of the Continental Shelf” (2010) 25 International Journal of Marine and Coastal Law 237, 258.

6 Barbados v. Trinidad and Tobago, note 4; Dispute Concerning Delimitation of the Maritime Boundary Between Bangladesh and Myanmar in the Bay of Bengal (Bangladesh/Myanmar) (Judgment of 14 March 2012), ITLOS Reports 2012, 4; In the Matter of the Bay of Bengal Maritime Boundary Arbitration (Bangladesh/India) (Award of 7 July 2014) (UNCLOS Annex VII Tribunal) Award, available at: https://pcacases.com/web/sendAttach/383 (accessed 30 September 2023); Dispute Concerning Delimitation of the Maritime Boundary between Ghana and Côte d’Ivoire in the Atlantic Ocean (Ghana/Côte d’Ivoire) (Judgment of 23 September 2017), ITLOS Reports 2017, 4; Dispute Concerning Delimitation of the Maritime Boundary between Mauritius and Maldives in the Indian Ocean (Mauritius/Maldives) (Judgment of 28 April 2023), ITLOS Reports 2022–2023 (to be published); Question of the Delimitation of the Continental Shelf Between Nicaragua and Colombia Beyond 200 Nautical Miles from the Nicaraguan Coast (Nicaragua v. Colombia) (Judgment of 13 July 2023) (ICJ).

7 Xuexia Liao, “Is There a Hierarchical Relationship between Natural Prolongation and Distance in the Continental Shelf Delimitation?” (2018) 33 International Journal of Marine and Coastal Law 79; Bjarni Már Magnússon, The Continental Shelf Beyond 200 Nautical Miles: Delineation, Delimitation and Dispute Settlement (Brill Nijhoff, 2015). However, although Magnússon supports the notion of a “single continental shelf,” he admits that “there are in law some differences between the continental shelf within and that beyond 200 nm.” Ibid, 137.

8 Michael Evans, “Maritime Boundary Delimitation” in Donald R. Rothwell, Alex Oude Elferink, Karen N. Scott et al., (eds), The Oxford Handbook of the Law of the Sea (Oxford University Press, 2015), 254, 265, note 58.

9 Barbados v. Trinidad and Tobago, note 4, [213].

10 See Bernard, note 5, 101.

11 Bangladesh/Myanmar, note 6, [361].

12 Ibid, [361].

13 Ibid, [363].

14 Bangladesh/Myanmar, note 6, Separate Opinion of Judge Cot, 190.

15 See the table of contents at ibid, 6.

16 Bangladesh/India, note 6, [77].

17 See the table of contents at ibid 4.

18 Bangladesh/India, note 6, [299].

19 Ibid, [404].

20 Ibid.

21 Bangladesh/India, note 6, [465].

22 Ibid, [437].

23 Ghana/Côte d’Ivoire, note 6, [490].

24 Ibid, [526].

25 See the table of contents at ibid, 5–6.

26 Mauritius/Maldives, note 6, [274].

27 Ibid. However, it must be noted that the Special Chamber did not take into consideration the Maldives’ claim of entitlement to a continental shelf beyond 200 NM within 200 NM of Mauritius in this context.

28 Ibid, [338–339].

29 Ibid, [340].

30 Ultimately, however, the Special Chamber decided not to proceed to delimit the continental shelf beyond 200 NM due to “significant uncertainty” concerning the natural prolongation of Mauritius. Ibid, [448–451].

31 Nicaragua v. Colombia, note 6, [75]. The Declaration of Judge Bhandari supports the notion of the “single continental shelf” and therefore questions whether the phrase “generally the same” should have been included as it “could potentially be read as diluting the notion of a ‘single continental shelf’” and “risks perpetuating uncertainty about the practical consequences of this notion.” Nicaragua v. Colombia, note 6, (Declaration of Judge Bhandari), [5–6].

32 Nicaragua v. Colombia, note 6, [74].

33 Hilde Woker, “Preliminary Reflections on the ICJ Judgment in Question of the Delimitation of the Continental Shelf Between Nicaragua and Colombia Beyond 200 Nautical Miles From the Nicaraguan Coast (Nicaragua v. Colombia) of 13 July 2023” 21 July 2023, EJIL:Talk! at: https://www.ejiltalk.org/preliminary-reflections-on-the-icj-judgment-in-question-of-the-delimitation-of-the-continental-shelf-between-nicaragua-and-colombia-beyond-200-nautical-miles-from-the-nicaraguan-coast-nicaragua-v-co (accessed 2 August 2023).

34 Question of the Delimitation of the Continental Shelf Between Nicaragua and Colombia Beyond 200 Nautical Miles From the Nicaraguan Coast (Nicaragua v Colombia) (Order of 4 October 2022) ICJ Reports 2022, 2.

35 Mauritius/Maldives, note 6, [57].

36 Alternatively, it could be viewed as a reference to the relationship between the exclusive economic zone (EEZ) and the continental shelf, thus posing the question of whether an entitlement to a continental shelf beyond 200 NM may extend within another coastal state’s entitlement to an EEZ (within 200 NM), rather than posing the question of whether an entitlement to a continental shelf beyond 200 NM may extend within another coastal state’s entitlement to a continental shelf within 200 NM. However, if that had been the Judges’ intention, would they not have explicitly referenced the EEZ in the questions?

37 Nicaragua v. Colombia, note 6, (Dissenting Opinion of Judge Charlesworth), [10]. See also generally the Dissenting Opinion of Judge Tomka.

38 Territorial and Maritime Dispute (Nicaragua v Colombia) (Judgment of 19 November 2012), ICJ Reports 2012, 624, [177]. The Court concluded that the continental shelf entitlement in this case would not be given effect, which is different from concluding that the entitlement did not exist at all. See also Nicaragua v. Colombia (Dissenting Opinion of Judge Charlesworth), note 38, [9].

39 Mauritius/Maldives, note 6, [274].

40 Ibid, [444] (emphasis added).

41 Ibid.

42 Nicaragua v. Colombia, note 6, [79].

43 Ibid, [86]. The Court made the same conclusions with respect to the islands of San Andrés and Providencia, and similar conclusions with respect to Serranilla and Baja Nuevo. Ibid, [91]; [99].

44 See ibid, [45]; [49–50]; [69–73]; [78].

45 Woker, note 33.

46 Nicaragua v. Colombia, note 6, [82].

47 See for example ibid, [75].

48 1982 UNCLOS, Art 76(1) (emphasis added).

49 See also D. N. Hutchinson, “The Concept of Natural Prolongation in the Jurisprudence Concerning Delimitation of Continental Shelf Areas” (1985) 55 British Yearbook of International Law 133, 184–185, who identifies seven different senses of the term “natural prolongation,” including a “basis of entitlement” in addition to referring to the entire region in which coastal states have sovereign rights, and Hyun Jung Kim, “Natural Prolongation: A Living Myth in the Regime of the Continental Shelf?” (2014) 45 Ocean Development & International Law 374, who distinguishes between three dimensions of natural prolongation: entitlement, delineation, and delimitation of the continental shelf.

50 This view seems to be supported by Bing Bing Jia, “The Notion of Natural Prolongation in the Current Regime of the Continental Shelf: An Afterlife?” (2013) 12 Chinese Journal of International Law 79.

51 North Sea Continental Shelf Cases (Federal Republic of Germany/Denmark; Federal Republic of Germany/Netherlands) (Judgment of 20 February 1969), ICJ Reports 1969, 3, [40].

52 Ibid, [4].

53 Ibid, [43].

54 Case Concerning the Continental Shelf (Libyan Arab Jamahiriya/Malta) (Judgement of 3 June 1985), ICJ Reports 1985, 3, [34].

55 Kim, note 53, 378, 381.

56 The Virginia Commentaries seem to endorse this view, evident from the diagram of Article 76, Satya N. Nandan and Shabtai Rosenne (eds), “Article 76—Definition of the Continental Shelf,” United Nations Convention on the Law of the Sea 1982: A Commentary Volume II (Martinus Nijhoff Publishers, 1993), 875.

57 This article is not concerned with the scholarly discussion surrounding the question of whether one basis of entitlement prevails over the other, as for example discussed in Liao, note 7; Davenport, note 5, 311–318. Rather, the fact that that discussion exists confirms the idea that there are indeed two alternative bases of entitlement.

58 Libya/Malta, note 58.

59 David A. Colson, “The Delimitation of the Outer Continental Shelf between Neighboring States Notes and Comments” (2003) 97 American Journal of International Law 91, 101. See also Jørgen Lilje-Jensen and Milan Thamsborg, “The Role of Natural Prolongation in Relation to Shelf Delimitation Beyond 200 Nautical Miles” (1995) 64 Nordic Journal of International Law 619, 622; Keith Highet, “The Use of Geophysical Factors in the Delimitation of Maritime Boundaries” (1993) 1 International Maritime Boundaries 176.

60 Fayokemi Olorundami, “Revisiting the Libya/Malta Decision and Assessing Its Relevance (or Otherwise) to the East China Sea Dispute” (2016) 15 Chinese Journal of International Law 717, 726. Libya/Malta, note 58, [40]; Colson, note 63, 103. However, Olorundami believes this division to be incorrect and states that “nowhere in the UNCLOS can the idea of inner and outer continental shelves be found” (despite evidence to the contrary as discussed below). Olorundami, note 64, 726.

61 Maritime Delimitation in the Indian Ocean (Somalia v. Kenya), Judgment ICJ Reports 2021, 206 (Individual Opinion, Partly Concurring and Partly Dissenting, of Judge Robinson), 326.

62 Ibid, [4].

63 Ibid, [5].

64 Ibid, [16].

65 See Davenport, note 5, 316, who states “there are two definitions of continental shelf, the distance-based continental shelf and the extended continental shelf.”

66 Libya/ Malta, note 58, (Dissenting Opinion of Judge Oda) [61].

67 Nicaragua v. Colombia, note 6, [65].

68 1982 UNCLOS, Art 76(8).

69 Nandan and Rosenne, note 60, 882–883; Signe Veierud Busch, “Law of the Sea Responses to Sea-Level Rise and Threatened Maritime Entitlements: Applying an Exception Rule to Manage an Exceptional Situation” in Elise Johansen, Signe Veierud Busch and Ingvild Ulrikke Jakobsen (eds), The Law of the Sea and Climate Change: Solutions and Constraints (Cambridge University Press, 2020), 309, 331–332.

70 1982 UNCLOS, Art 76(4).

71 ‘Final Act of the Third United Nations Conference on the Law of the Sea, note 3, Annex II.

72 Ibid. The SoU was developed to apply to the southern part of the Bay of Bengal, but the special circumstances may also be present in other areas, such as Myanmar and Kenya. It is at this stage in time uncertain whether those coastal states (beyond the Bay of Bengal) would also be allowed to refer to the SoU to determine the outer edge of the continental margin. See Lindsay Parson, “Annex II to the Final Act” in Alexander Proelss (ed), United Nations Convention on the Law of the Sea: A Commentary (BECK, 2017), 600; Ray Wood and Elana Geddis, “Technical and Legal Challenges of the Statement of Understanding,” ABLOS X: Opportunities and Challenges in the Governance of the Planet Ocean (2019), https://iho.int/en/ablos10-conference-2019, accessed 27 February 2023.

73 See also Joanna Mossop, The Continental Shelf Beyond 200 Nautical Miles: Rights and Responsibilities (Oxford University Press, 2016), 241, where she considers that “although many of the legal considerations in relation to the extended continental shelf are not significantly different than within 200 nm […] there are some important respects in which the legal regime applying to the extended continental shelf needs separate consideration.”

74 1982 UNCLOS, Art 82(1).

75 Evans, note 8, 265, note 59.

76 1982 UNCLOS, Art 82(3).

77 Evans, note 8, 265, note 59.

78 1982 UNCLOS, Art 246(5).

79 1982 UNCLOS, Art 246(6).

80 Shabtai Rosenne and Alexander Yankov (eds), “Article 246—Marine Scientific Research in the Exclusive Economic Zone and on the Continental Shelf,” United Nations Convention on the Law of the Sea 1982: A Commentary Volume IV (Martinus Nijhoff Publishers, 1991), 519 (emphasis added).

81 Ibid.

82 The idea that the three-stage approach may not be applicable to delimitation of the continental shelf beyond 200 NM finds some support in the literature: for example, Liao, note 7, 111–115; Davenport, note 5, 320; Jianjun Gao, “The Okinawa Trough Issue in the Continental Shelf Delimitation Disputes Within the East China Sea” (2010) 9 Chinese Journal of International Law 143, 169–177.

83 Leonardo Bernard and Clive Schofield, “Disputes Concerning the Delimitation of the Continental Shelf Beyond 200 Nautical Miles” in Tomas Heidar (ed), New Knowledge and Changing Circumstances in the Law of the Sea (Brill Nijhoff, 2020), 157, 174; Massimo Lando, Maritime Delimitation as a Judicial Process (Cambridge University Press, 2019), 134–135.

84 1982 UNCLOS, Art 83(1). This wording is also used in Article 74 on the delimitation of the EEZ.

85 Maritime Delimitation in the Black Sea (Romania v. Ukraine) Judgment, ICJ Reports 2009, 61, [116]. There is juridical precedent for not using the provisional equidistance line. In the Nicaragua/Honduras case, the ICJ found that an equidistance line did not produce an equitable outcome, and instead applied the angle bisector method. It concluded that “the equidistance method does not automatically have priority over other methods of delimitation and, in particular circumstances, there may be factors which make the application of the equidistance method inappropriate.” Case Concerning Territorial and Maritime Dispute Between Nicaragua and Honduras in the Caribbean Sea (Nicaragua v. Honduras), Judgment, ICJ Reports 2007, 659, [272]. Indeed, in this case, the ICJ found that it was “impossible” to construct a provisional equidistance line. Ibid, [280].

86 Maritime Delimitation in the Black Sea (Romania v. Ukraine), note 63, [116].

87 Ibid, [120].

88 Ibid, [122].

89 See Erik Franckx, “A Single Maritime Boundary: From UNCLOS III to Present-Day Developments” (2023) 148 Marine Policy 105425.

90 Liao, note 7, 111. See also Bernard and Schofield, note 87, 168–169; Giovanny Vega-Barbosa, “Outer Continental Shelf Delimitation in the Western Caribbean Sea (Nicaragua v. Colombia II): What Lessons to Learn from the East China Sea Dispute on the Viability of Maritime Delimitation Between Different Bases of Continental Shelf Entitlement?” (2019) 47 Revista da Faculdade de Direito da Universidade Federal de Uberlândia 92.

91 Dispute Concerning Delimitation of the Maritime Boundary Between Mauritius and Maldives in the Indian Ocean (Mauritius/Maldives) Memorial of Mauritius (25 May 2021), [4.70].

92 Ibid, [4.71].

93 Ibid, [4.72]. Technically, one of the constraint lines includes a reference to the distance from the coast.

94 Ibid, [4.73].

95 Nicaragua v. Colombia, note 6 (Separate Opinion of Judge Xue), [57].

96 Liao, note 7, 111–115.

97 Mauritius/Maldives, Memorial of Mauritius, note 95, [4.73]. This had also been argued by Nicaragua in its earlier case with Colombia. Territorial and Maritime Dispute (Nicaragua v. Colombia) Reply of Nicaragua Volume I (2009), [3.46].

98 Mauritius/Maldives, Memorial of Mauritius, note 95, [4.73].

99 This argument had been put forward by the Maldives; see Mauritius/Maldives, note 6, [277].

100 As had been suggested by Nicaragua in its earlier case with Colombia, see Territorial and Maritime Dispute (Nicaragua v. Colombia) Verbatim Record CR 2012/9, [75].

101 Chris Carleton, “Delimitation Issues” in Peter J. Cook and Chris Carleton (eds), Continental Shelf Limits: The Scientific and Legal Interface (Oxford University Press, 2000), 312, 316. Despite the general lack of recognition of geophysical factors in delimitations to date, in the delimitation between Australia and New Zealand, geophysical factors were “influential” for portions of the delimitation beyond 200 NM. Bernard and Schofield, note 87, 175.

102 1982 UNCLOS, Art 83(1).

103 Bangladesh/Myanmar, note 6, [225].

104 See Thomas Cottier, Equitable Principles of Maritime Boundary Delimitation: The Quest for Distributive Justice in International Law (Cambridge University Press, 2015), 199–203.

105 Bernard, note 5, 101.

106 Ibid, 109.