1 Question of the Delimitation of the Continental Shelf Between Nicaragua and Colombia Beyond 200 Nautical Miles from the Nicaraguan Coast (Nicar. v. Colom.), Judgment (July 13, 2023), https://www.icj-cij.org/case/154/judgments [hereinafter 2023 judgment].

2 In Mauritius/Maldives, the Special Chamber of ITLOS had the opportunity to answer this same question but it declined to do so as it considered that after delimiting with a single maritime boundary the exclusive economic zones and continental shelves within 200 nautical miles between the Parties, the boundary rendered “moot” the question of delimitation of the overlapping area between the claim of the Maldives to an extended continental shelf and the claim of Mauritius to a 200 nautical mile zone. See Dispute concerning delimitation of the maritime boundary between Mauritius and Maldives in the Indian Ocean (Mauritius/Maldives), ITLOS Case No. 28, Judgment (28 April 2023), ¶ 274. As for other cases, the ICJ itself as well as other international courts and tribunals have dealt with the issue of the delimitation of the extended continental shelf but between states with adjacent coasts. See, e.g., Delimitation of the Maritime Boundary in the Bay of Bengal (Bangl./Myan.), Judgment, 2012 ITLOS Rep. 4; Bangladesh v. India, Perm. Ct. Arb., Judgment (July 7, 2014); Maritime Delimitation in the Indian Ocean (Som. v. Ken.), Judgment (Oct. 12, 2021).

3 Territorial and Maritime Dispute (Nicar. v. Colom.), Judgment, 2012 I.C.J. Rep. 624, ¶¶ 17.I(3), 119, 121 (Nov. 19) [hereinafter 2012 Judgment]. Conversely, the ICJ delimited the territorial sea, the exclusive economic zone and the continental shelf within 200 nautical miles between the two countries.

4 The ICJ recalled that “any claim of continental shelf rights beyond 200 nautical miles [by a state Party to UNCLOS] must be in accordance with Article 76 of UNCLOS and reviewed by the CLCS established thereunder” (Id. ¶ 126). In this respect, the ICJ observed that Nicaragua had submitted to the CLCS only “Preliminary Information,” and thus Nicaragua did not meet the requirements for information on the limits of the extended continental shelf which shall be submitted by the coastal states to the CLCS in accordance with Article 76(8) of UNCLOS (Id. ¶ 127).

5 Id. ¶¶ 129, 130, 131.

6 2023 Judgment, supra note 1, ¶ 25.

7 Id. ¶ 26.

8 Unlike Nicaragua, Colombia is not a Party to UNCLOS. Thus, only customary international law as reflected in UNCLOS was applicable to the case at hand (Id. ¶¶ 44, 45).

9 Before examining any technical and scientific questions, the ICJ considered necessary to decide on certain questions of law. By Order dated 4 October 2022, the ICJ decided to bifurcate the proceedings on the merits requesting the parties to focus its oral pleadings on two questions: (1) “Under customary international law, may a State's entitlement to a continental shelf beyond 200 nautical miles from the baselines from which the breadth of its territorial sea is measured extend within 200 nautical miles from the baselines of another State?;” and (2) “What are the criteria under customary international law for the determination of the limit of the continental shelf beyond 200 nautical miles from the baselines from which the breadth of the territorial sea is measured and, in this regard, do paragraphs 2 to 6 of Article 76 of the United Nations Convention on the Law of the Sea reflect customary international law?” (Question of the Delimitation of the Continental Shelf between Nicaragua and Colombia beyond 200 Nautical Miles from the Nicaraguan Coast (Nicar. v. Colomb.), Order, 2022 I.C.J. Rep. 563–565).

10 2023 Judgment, supra note 1, ¶ 70. See also Continental Shelf (Libyan Arab Jamahiriyia/Malta), Judgment, 1985 I.C.J. Rep. ¶¶ 33, 34.

11 Recalling its previous jurisprudence, the ICJ noted that Articles 56, 58, 61, 62 and 73 of UNCLOS lying down rights and duties of both coastal states and other states in the EEZ reflect customary international law (2023 Judgment, supra note 1, ¶ 69). See Alleged Violations of Sovereign Rights and Maritime Spaces in the Caribbean Sea (Nicar. v. Colomb.), Judgment (April 21, 2022), ¶ 57.

12 2023 Judgment, supra note 1, ¶ 70.

13 Id.

14 A “grey area” is “an area [that] results when a delimitation line which is not an equidistance line reaches the outer limit of one State's exclusive economic zone and continues beyond it in the same direction, until it reaches the outer limit of the other State's exclusive economic zone.” (Delimitation of the Maritime Boundary in the Bay of Bengal (Bangl./Myan.), Judgment, 2012 ITLOS Rep. 4, ¶ 464). “The delimitation of the continental shelf beyond 200 nm gives rise to an area of limited size located beyond 200 nm from the coast of Bangladesh but within 200 nm from the coast of Myanmar, yet on the Bangladesh side of the delimitation line” (Id. ¶ 463).

15 Delimitation of the Maritime Boundary in the Bay of Bengal (Bangl./Myan.), Judgment, 2012 ITLOS Rep. 4; Bangladesh v. India, Perm. Ct. Arb., Judgment (July 7, 2014), https://pca-cpa.org/en/cases/18.

16 2023 Judgment, supra note 1, ¶ 72.

17 Id.

18 Id. ¶ 75.

19 Id. ¶ 76.

20 Id.

21 Id.

22 Id.

23 Colombia had argued that out of 93 submissions to the CLCS, 55 submissions could have extended within the 200-nautical mile zones of other states; 51 of those 55 stopped at the 200-nautical-mile entitlements of neighbouring states when those submissions could have gone further on technical grounds. See 2023 Judgment, Verbatim Record, CR 2022/26, 33–34 (Dec. 6, 2022) (Agent of Colombia).

24 Id. ¶ 77. In addition, the ICJ noted that only few states have claimed, in their submissions to the CLCS, an extended continental shelf encroaching on “maritime areas within 200 nautical miles” of other states and that in those situations, the states concerned had objected to those submissions (Id.). In relation to the practice of the small number of coastal states non-parties to UNCLOS, the ICJ stated that it was not aware of any state that had claimed an extended continental shelf extending within 200 nautical miles from the baselines of another state (Id.).

25 Id.

26 Id.

27 Id. ¶ 79. Through its 2023 Judgment, the ICJ mentions that a state's entitlement to an extended continental shelf cannot extend within 200 nautical miles from the baseline of another state. The judgment confirms however that a state's entitlement to an extended continental shelf may not extend within another state's entitlement to a continental shelf within 200 nautical miles (Id. ¶ 82). The ICJ might have used the expression “within 200 nautical miles from the baselines of another State” to keep consistency with the idea of the “inseparability” between the EEZ and the continental shelf within 200 nautical miles that the ICJ itself and other international tribunals have upheld.

28 Id. ¶¶ 80–82.

29 The ICJ determined that it could not proceed to the delimitation of the maritime boundary as requested by Nicaragua since, under customary international law, Nicaragua is not entitled to an extended continental shelf within 200 nautical miles from the baselines of Colombia's main coast, and thus there is no overlapping entitlement to be delimited. This regardless of the technical and scientific considerations (Id. ¶¶ 85–87). For the same reasons, the ICJ also determined that it could not delimit the maritime boundary between Nicaragua's extended continental shelf and the continental shelf within 200 nautical miles from the baselines of the coasts of San Andrés and Providencia, two islands belonging to Colombia (Id. ¶¶ 90–92). Finally, with respect to the effect, if any, of the maritime entitlements of Serranilla and Bajo Nuevo (three maritime features under Colombia's sovereignty) on any remaining maritime delimitation between Nicaragua and Colombia, the ICJ concluded that, regardless of the maritime zones generated by Serranilla and Bajo Nuevo, there could be no area of overlapping entitlement to a continental shelf to be delimited. If those maritime features were entitled to an EEZ and a continental shelf, Nicaragua's extended continental shelf may not extend into the 200-nautical mile maritime entitlements of those islands. Conversely, if Serranilla and Bajo Nuevo did not generate an EEZ and a continental shelf, they would not have any maritime entitlements in the area in which Nicaragua asserts an extended continental shelf (Id. ¶¶ 93, 97–100).

30 Id. ¶¶ 80–82. Accordingly, the ICJ did not pronounce itself either on whether Article 76 paragraphs 2–7 of UNCLOS reflected customary international law.

31 See Evans Malcolm and Nicholas A. Ioannides, The International Court of Justice and the Law of the Sea Dispute Settlement System, in Research Handbook on the International Court of Justice (Achilles Skordas and Lisa Mardikian eds., Forthcoming (both authors agree with the rule of customary law identified in the 2023 Judgment, but criticise the ICJ for not elaborating on the broader potential implications of that rule, in particular with regards to maritime delimitation), https://ssrn.com/abstract=4514860). See also 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, EJIL: Talk! (July 21, 2023), 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/; Matei Alexianu, The Nicaragua v. Colombia Continental Shelf Judgment: Short but Significant, 27(9) ASIL INSIGHTS (Sept. 29, 2023), https://www.asil.org/insights/volume/27/issue/9.

32 In the operative part of its judgment, the ICJ decided by thirteen votes in favor to four against on rejecting Nicaragua's request for delimitation and by twelve votes in favor to five against on rejecting Nicaragua's request with respect to the maritime entitlements of Serranilla and Bajo Nuevo (Colombia's maritime features). Judges Tomka, Robinson, Charlesworth and Judge ad hoc Skotnikov appended dissenting opinions while Judges Xue, Iwasawa, and Nolte appended separate opinions. Judge Bhandari appended a declaration.

33 Besides this issue, critics of the judgment have casted doubt on whether the practice of states examined by the ICJ could be considered as general state practice, but even then, they have recognised that in spite of “not being perfect,” this practice could be considered a general one. Judge Tomka observed that “the Judgment does not acknowledge, much less analyse, the existence of contrary State practice whereby States have claimed a continental shelf entitlement that extends within 200 nautical miles from the baselines of another State” (2023 Judgment, supra note 1, Dissenting Opinion of Judge Tomka, ¶ 45). However, he also stated that “[s]ome inconsistencies and contradictions are not necessarily fatal to a finding of ‘a general practice’ [and] that for some States, practice varies and should arguably be given less weight” (Id. ¶ 49). See also Id. Dissenting Opinion of Judge Robinson, ¶¶ 12, 13; Id. Dissenting Opinion of Judge Charlesworth, ¶ 26. It is also worth noting that the ICJ seems to rely on the objective element (state practice) rather than the subjective element (opinio juris) to find the customary rule. The ICJ also seems to justify the existence of this rule based on its interpretation of the travaux préparatoires and the logic behind the EEZ and continental shelf regimes.

34 Id. Dissenting Opinion of Judge Tomka, ¶ 59; Id. Separate Opinion of Judge Xue, ¶ 47; Id. Dissenting Opinion of Judge Robinson, ¶ 19. Judge Tomka elaborated on the alternative motives that could explain the state practice (Id. Dissenting Opinion of Judge Tomka, ¶¶ 53-56).

35 See Rule 46 of the Rules of Procedure of the CLCS, Annex I, paragraph 5(a): “In cases where a land or maritime dispute exists, the Commission shall not consider and qualify a submission made by any of the States concerned in the dispute. However, the Commission may consider one or more submissions in the areas under dispute with prior consent given by all States that are parties to such a dispute.”

36 See Delimitation of the Maritime Boundary in the Bay of Bengal (Bangl./Myan.), Judgment, 2012 ITLOS Rep. 4, ¶¶ 386–392.

37 See Sir Malcolm D. Evans and Nicholas A. Ioannides, A Commentary on the 2023 Nicaragua v Colombia case, EJIL: Talk! (Aug. 4, 2023), https://www.ejiltalk.org/a-commentary-on-the-2023-nicaragua-v-colombia-case/; H.J. Woker, Challenging the Notion of a “Single Continental Shelf,” in Ocean Dev. & Int'l L. (2023), https://doi.org/10.1080/00908320.2023.2271393.

38 See, e.g., Sir Malcolm D. Evans and Nicholas A. Ioannides, supra note 37.

39 In the Bangladesh/Myanmar case, for instance, ITLOS acknowledged the existence of “grey areas” as a consequence of delimitation of the overlapping area of the Parties' continental shelves and concluded that both the EEZ and the continental shelf legal regimes can coexist, and each coastal state must exercise its rights and perform its duties with due regard to the rights and duties of the other, Bangladesh in its extended continental shelf and Myanmar in the superjacent waters (Delimitation of the Maritime Boundary in the Bay of Bengal (Bangl./Myan.), Judgment, 2012 ITLOS Rep. 4, ¶¶ 471, 474, 475).

40 2023 judgment, supra note 1, Dissenting Opinion of Judge Tomka, ¶ 67.

41 Id. ¶ 38. He added that delimitation could result in maritime areas in which jurisdiction over the EEZ is adjudicated to one state and jurisdiction over the continental shelf to another (Id. ¶ 72).

42 Id. Separate Opinion of Judge Xue, ¶ 27.

43 If there is no overlapping of entitlements, there is no need for delimitation. If there is no need for delimitation, the potential existence of “grey areas” is avoided ab initio.

44 ITLOS had addressed the consequences of the “grey area” that resulted from delimitation by asserting that the states concerned should cooperate to determine the measures that they consider appropriate to ensure that each of them exercise its rights and perform its duties with due regard to the rights and duties of the other (Delimitation of the Maritime Boundary in the Bay of Bengal (Bangl./Myan.), Judgment, 2012 ITLOS Rep. 4, ¶¶ 475, 476).

45 See Matei Alexianu, supra note 31, at 5–6.

46 See Sir Malcolm D. Evans and Nicholas A. Ioannides, supra note 37.