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对 200 海里以外的大陆架权利的新限制？– 近期判例法的影响
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对 200 海里以外的大陆架权利的新限制？– 近期判例法的影响

于The International Journal of Marine and Coastal Law
著者：
Hilde Woker Assistant Professor of Public International Law, Leiden University Leiden Netherlands

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https://orcid.org/0000-0001-5960-5934
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Leonardo Bernard Senior Lecturer, Australian National Centre for Ocean Resources and Security, University of Wollongong Wollongong Australia

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在线出版日期:
16 Aug 2024
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关键词continental shelf; 200 nautical miles; entitlement; Commission on the Limits of the Continental Shelf; International Court of Justice

Introduction

Many coastal States worldwide assert their rights to an exclusive economic zone (EEZ) and continental shelf that extends up to 200 nautical miles (M) from their baselines. Many of these nations also assert a continental shelf that stretches beyond the 200 M limit.1 The 1982 United Nations Convention on the Law of the Sea (LOS Convention or the Convention)2 allows coastal States with broad continental shelves to assert sovereign rights to shelf resources on their continental margin, but no further than 350 M from their coastlines or up to 100 M from the 2,500-metre isobath.3 These entitlements are commonly referred to as the ‘outer continental shelf’.4 Such assertions on the part of coastal States must be submitted to and reviewed by a special body established under the LOS Convention called the Commission on the Limits of the Continental Shelf (CLCS).5 Any continental shelf entitlement seawards of 200 M must be delineated based on the recommendations of the CLCS.

In certain scenarios, the entitlement of the continental shelf of one coastal State beyond 200 M might encroach within 200 M of another State. This situation creates the need to balance different entitlements and raises the problem of interaction and even potential delimitation between these overlapping entitlements. This was exactly the situation between Nicaragua and Colombia, and Mauritius and the Maldives to a certain degree, both of which were the subject of recent decisions by the International Court of Justice (ICJ) and a special chamber of the International Tribunal for the Law of the Sea (ITLOS) respectively.6

The judgment in the case involving Mauritius and the Maldives came a couple of months before the Nicaragua v. Colombia judgment, and it might have served as an early indication of what was to unfold in the latter situation. The case was initiated in 2019 when it was brought before the special chamber of ITLOS, where the Chamber was asked to delimit the parties’ EEZ and continental shelf within 200 M and outer continental shelf. The Maldives contended that an area of overlap existed between its claim to a continental shelf extending beyond 200 M and Mauritius’ claim to a 200 M EEZ and continental shelf in the same region. Mauritius contested the assertion that the Maldives’ entitlement to an outer continental shelf could intrude within the 200 M boundary of Mauritius. Indeed, the President of the ITLOS Special Chamber had asked the parties to elaborate on their positions concerning this question.7 Nevertheless, the Special Chamber sidestepped this issue by establishing the boundaries of the EEZ and continental shelves within 200 M for both parties through a single maritime boundary. Consequently, neither party can assert or exert sovereign authority or jurisdiction over the EEZ or continental shelf situated within the 200 M limit of the other party, as situated on the other side of the determined boundary. Thus, this boundary effectively rendered moot the matter of determining the extent of the overlap between the Maldives’ claim to a continental shelf beyond 200 M and Mauritius’ claim to a 200 M zone.8

In the context of delimiting both parties’ outer continental shelf entitlements, the parties disagreed on whether Mauritius has an entitlement to a continental shelf beyond 200 M.9 Mauritius had presented various routes of natural prolongation, one of which passed through the Maldives’ continental shelf within 200 M which was uncontested by Mauritius (Figure 1). However, according to the Special Chamber, these routes ‘cannot form a basis for Mauritius’ … entitlement to the continental shelf beyond 200 [M]’.10 The Special Chamber stipulated that a coastal State ‘cannot validly claim’ an entitlement to an outer continental shelf ‘based on the natural prolongation through another State’s uncontested continental shelf’.11

Figure 1
Figure 1

Image reproduced from the counter-memorial of the Maldives depicting one of the routes of natural prolongation relied upon by Mauritius, traversing through the 200-M zone of the Maldives (Dispute concerning delimitation of the maritime boundary between Mauritius and Maldives in the Indian Ocean (Mauritius/Maldives), ITLOS, Counter-memorial of Maldives, Figure 9, at p. 43)

Citation: The International Journal of Marine and Coastal Law 2025; 10.1163/15718085-bja10193

In contrast to the approach taken by ITLOS, the ICJ had to confront the matter of overlapping entitlements directly. In this case, Nicaragua asserted that its continental shelf extends beyond 200 M, which overlaps with Colombia’s own 200 M continental shelf and EEZ from its coastline. Although Nicaragua is a State Party to the LOS Convention, Colombia is not, which means that the cases between them are decided based on customary international law rather than treaty law. Nicaragua had previously approached the ICJ to resolve the issue of delimiting the ‘shared continental shelf’ with Colombia.12 However, in 2012, the ICJ determined that it could not proceed with this delimitation because Nicaragua had not yet demonstrated that its entitlement to a continental shelf extended far enough to intersect with Colombia’s 200 M continental shelf and EEZ entitlement.13 Subsequently, the ICJ clarified14 that it rejected Nicaragua’s claim due to Nicaragua having yet to discharge its obligation under the LOS Convention, which required submitting information about its continental shelf beyond 200 M to the CLCS,15 and that ‘Nicaragua had to submit such information as a prerequisite for the delimitation’ of the continental shelf beyond 200 M by the Court.16 Following this decision, on 24 June 2013, Nicaragua finally presented information to the CLCS concerning the outer limits of its continental shelf beyond 200 M. Then, on 16 September 2013, Nicaragua once again sought the ICJ’s intervention to establish the boundary of the overlapping continental shelf between the two nations (Figure 2).

Figure 2
Figure 2

Image reproduced from the 2023 ICJ judgment depicting Colombia’s 200-M zone, and Nicaragua’s asserted outer limits of its continental shelf within that zone (Question of the Delimitation of the Continental Shelf Between Nicaragua and Colombia Beyond 200 Nautical Miles from the Nicaraguan Coast (Nicaragua v. Colombia), ICJ, Judgment, 13 July 2023, at p. 18)

Citation: The International Journal of Marine and Coastal Law 2025; 10.1163/15718085-bja10193

Colombia contested the jurisdiction of the ICJ to address the case, inter alia, since the CLCS had not issued any recommendations concerning Nicaragua’s outer continental shelf limits beyond 200 M. In response, the ICJ differed from Colombia’s stance and clarified that, as a State party to the Convention, Nicaragua’s obligation solely involves communicating information about the extent of its continental shelf beyond 200 M to the CLCS. The actual act of making recommendations rests within the authority of the CLCS.17 The ICJ also emphasised that the role of the CLCS is specifically associated with defining the outer boundaries of the continental shelf, not with the task of boundary delimitation.18 The ICJ’s position was that the delimitation of overlapping entitlements to the continental shelf beyond 200 M could be carried out independently of any recommendations from the CLCS. Furthermore, the ICJ stressed that receiving a recommendation from the CLCS is not a prerequisite that needs to be fulfilled before Nicaragua could seek the ICJ’s involvement in resolving a dispute related to such delimitation.19 Thus, the ICJ concluded that it had jurisdiction to hear the case and that it was admissible.

After the parties had submitted their written pleadings, the ICJ in 2022 requested the disputing parties to focus their oral arguments on the merits solely on two specific 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?

  • (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?20

On 13 July 2023, the ICJ issued a judgment that established, according to customary international law, that a State’s entitlement to a continental shelf beyond 200 M cannot encroach upon the zone within 200 M from another State’s baselines.21 Regardless of the criteria used to define the outer limits of a State’s outer continental shelf, the ICJ declared that the outer continental shelf cannot overlap with the continental shelf area within 200 M of another State’s baselines.22 As a result of this decision, the ICJ concluded that Nicaragua is not entitled to an extended continental shelf within 200 M from the baselines of Colombia’s mainland coast. Consequently, within 200 M of Colombia’s mainland coast and islands, there is no area where entitlements overlap and delimitation is required.23

The ICJ’s judgment has already received critical commentary, both from academic authors24 as well as its dissenting judges.25 The main point of critique is the fragile foundation of the Court confirming a rule of customary international law. The Court’s ruling is based on its assessment that there exists adequate State practice and opinio juris supporting the assertion that in customary international law, a continental shelf entitlement beyond 200 M should not encroach upon the 200 M of another State.26 The State practice (and opinio juris) upon which the Court’s conclusion rests consists of submissions to the CLCS.27 However, these submissions are not recognitions of the outer limits of a continental shelf per se. Although many States have indeed refrained from submitting information within 200 M of another State, there are questions on whether States refrained from encroaching within 200 M of another State due to a perceived legal obligation or simply as a matter of choice driven by other considerations.28 This particular discussion falls beyond the scope of this article, yet it casts doubt on the jurisdictional value of the decision that warrants future in-depth examination.

Both rulings, with particular emphasis on the latter, have the potential to reshape our understanding of Articles 76, 77, and 83 of the LOS Convention. These decisions not only redefined the interplay between the continental shelf extending beyond 200 M on the one hand, and the EEZ and continental shelf within 200 M on the other, they also brought into question the intricate relationship between the processes of delineation and delimitation. Moreover, the recent case law has introduced a new constraint to the entitlement to a continental shelf beyond 200 M. Furthermore, these judgments hold significant implications for the concept of a ‘single continental shelf’ and raise questions about the necessity of establishing grey areas in the future and the applicable delimitation methodology. This article will thoroughly explore all these matters.

Relationship between Various Entitlements within and beyond 200 M

According to the two judgments summarised above, a coastal State’s entitlement to an outer continental shelf may not extend within 200 M of another coastal State. Despite the fragile foundation of that conclusion, the question is what would negate such an outer continental shelf entitlement within 200 M of another State? Is it primarily the other State’s inherent entitlement to a continental shelf within 200 M, or does it hinge on the presence of a distance-based EEZ claim, which also encompasses the seabed and subsoil within 200 M? The recent case law does not give us an easy answer to this question.

The questions posed by the ICJ and the Special Chamber of ITLOS simply refer to an area ‘within 200 nautical miles from the baselines of another State’ and the ‘200 nautical miles limit’.29 Within 200 M from the baselines, a coastal State has sovereignty over the territorial sea (up to 12 M), specific enforcement jurisdiction over the contiguous zone (from 12–24 M from the baselines), and sovereign rights and jurisdiction over the continental shelf and within the EEZ (if claimed). It is the latter two zones that have the potential to negate the existence of an outer continental shelf entitlement within the entirety of the 200 M limit of another State. The ICJ’s judgment in Nicaragua v. Colombia discusses the EEZ and its relationship to the continental shelf at length. This implies that perhaps it is the EEZ that negates an outer continental shelf entitlement within 200 M of another State. However, the Court ultimately concludes that a State’s ‘extended continental shelf cannot overlap with the area of continental shelf within 200 nautical miles from the baselines of another State’.30 Furthermore, the ITLOS Special Chamber dismissed a route of natural prolongation traversing through another State’s ‘uncontested continental shelf   ’.31 Nonetheless, neither judicial body clearly articulated which of those two zones – EEZ or continental shelf (within 200 M) – negates the existence of an outer continental shelf entitlement. This unclarity is somewhat problematic, as one of those two is inherent,32 whereas the other needs to be claimed expressly.

In an attempt to address this question comprehensively, we must analyse the interplay between the continental shelf and the EEZ, with a specific focus on the continental shelf’s division into the ‘inner’ continental shelf within 200 M and the ‘outer’ continental shelf beyond 200 M. This section will explore the dynamics between the inner and outer continental shelf and examine the relationship between the outer continental shelf and the EEZ. Before delving into these aspects, it is essential to recognise that these relationships manifest in two distinct scenarios: firstly, within the context of one State’s entitlements to maritime zones, and secondly, in the interaction between the entitlements of one State and those of another State. This article primarily concentrates on the latter relationship – how the entitlements of one State interact with those of another. However, it remains crucial to acknowledge the relationship within the context of one State’s entitlement to maritime zones, which is briefly touched upon below.

As previously mentioned, a coastal State is entitled to an inner continental shelf extending up to 200 M from the baseline, and in some cases, to an outer continental shelf that extends to the edge of the continental margin. While there are apparent distinctions between the continental shelf within 200 M and the one extending beyond this limit,33 the concept of a ‘single continental shelf’ has gained prominence following its introduction by an arbitral tribunal in 2006 as a means to reject the notion of an inner and a separate outer continental shelf.34 However, if there is such a thing as a ‘single continental shelf’, why would the outer part of that entitlement be negated by another State’s inner entitlement? The present authors have extensively argued that it is now imperative to move beyond the inaccurate notion of a ‘single continental shelf’ and instead recognise that the inner and outer continental shelves are distinct from one another.35 Only then is it possible to envisage a situation in which a continental shelf within 200 M may negate another State’s entitlement to a continental shelf beyond 200 M. Although the continental shelf, as a whole, is inherent as per Article 77(3), it is clear there are some notable differences between the continental shelf within and beyond 200 M, and that the coastal State has a stronger degree of sovereign rights and jurisdiction within 200 M than it does beyond that limit.

Regarding the relationship between a State’s EEZ and its continental shelf within 200 M, extensive discourse has revolved around whether one regime takes precedence over the other, or if one regime has subsumed the other within its framework.36 However, it is evident, through a careful examination of the provisions and the historical context of the LOS Convention, as well as through an analysis of State practice and the precedents established by international courts and tribunals after the adoption of the LOS Convention, that the EEZ has not absorbed the continental shelf regime.37 Instead, these two regimes coexist in an integrated manner.38 The retention of both these regimes within the LOS Convention serves the purpose of ensuring that all economic resources within 200 M fall under the jurisdiction of the coastal State, while simultaneously safeguarding the pre-existing shelf rights established under the 1958 Convention on the Continental Shelf and customary international law.39

Now that we have established that within a single State’s entitlements up to 200 M from the baselines, the EEZ and continental shelf regimes coexist but maintain their separate identities and that there exists a clear distinction between the outer and inner continental shelf, we can now shift our focus to exploring how one State’s entitlement to an outer continental shelf interacts with another State’s entitlement to an EEZ and an inner continental shelf and how possibly the latter may negate the existence of the former. Here, it proves challenging to examine the interaction between one State’s outer continental shelf and another State’s inner continental shelf without considering the latter’s entitlement to an EEZ. This is because the rights held by a State over its inner continental shelf would likewise extend to the seabed and subsoil within any EEZ it might declare.40

Even though natural prolongation and distance are considered as two different bases for entitlement to a continental shelf within 200 M, the ICJ stated that in cases where the continental margin does not extend beyond 200 M, ‘natural prolongation’ is ‘in part defined by the distance from the shore, irrespective of the physical nature of the intervening sea-bed and subsoil’.41 This means that in areas where the coasts of two or more coastal States are not more than 400 M apart, the ‘title [for an EEZ and continental shelf] depends solely on the distance from the coasts’.42 This decision has been considered a ‘significant turning point’,43 as between coasts not more than 400 M apart, distance as a basis of entitlement takes precedence over any potential entitlement based on scientific criteria.44 An arbitral tribunal subsequently also concluded that, within 200 M, the concept of distance as a newfound basis of entitlement became ‘intertwined’ with that of natural prolongation.45

Since for both the EEZ and inner continental shelf distance is the primary basis of entitlement within 200 M, it is still unclear if it is one of those zones or both that negates another State’s outer continental shelf. The ICJ in Nicaragua v. Colombia did not differentiate between Colombia’s entitlements within 200 M that might negate Nicaragua’s outer continental shelf. Instead, its decision was predicated on both aspects.46 The Court reinforced the notion that the legal frameworks governing the EEZ and the continental shelf of a coastal State within 200 M of its baselines are interconnected.47 Indeed, the ICJ was careful to say that the outer continental shelf of a State cannot exist within the 200 M of another State, without mentioning the EEZ. In other words, it seems that either the EEZ or the inner continental shelf would negate the existence of an outer continental shelf entitlement, regardless of the nature of that zone.48 This would mean that even if a State did not claim a full EEZ, the 200 M distance mark of that State would stop the entitlement of an outer continental shelf of another State. In any event, the Court’s finding that entitlement to an outer continental shelf cannot overlap with an entitlement within 200 M in an area where the coasts are more than 400 M apart is a significant change in practice. As Judge Robinson submits, the ICJ’s judgment ‘strikes a jangling, discordant note in the otherwise harmonious relationship between the various maritime zones in the law of the sea’.49

Re-thinking the Relationship between Delineation and Delimitation

Another reason why the recent case law is significant is because it forces us to reconsider the relationship between delineation and delimitation. In essence, there are two ways of viewing this relationship. One is according to a legal purist perspective, in which delineation and delimitation are completely different concepts. The other is a more realistic perspective, according to which one recognises that these two processes are already intertwined. Both perspectives are discussed below.

Following a legal purist perspective, delineation and delimitation are two separate and, more importantly, independent processes. Delineation refers to the unilateral measurement of the extent of a coastal State’s continental shelf, whereas delimitation refers to the division of areas of overlapping entitlements of two or more States. As Judge Charlesworth explains in her dissenting opinion, the question of entitlement to an outer continental shelf is ‘distinct from, albeit complementary to, the question of maritime delimitation’, and these two questions ‘are governed by different legal rules, and they can give rise to separate disputes’.50 As these two procedures remain separate, coastal States should retain the freedom to establish the outermost boundaries of their maritime zone entitlements without having to consider the entitlements of other States.

It is important to remember that delineation is, in essence, a unilateral procedure, unlike delimitation. The delineation of the continental shelf is governed by Article 76 of the LOS Convention, whereas delimitation is dealt with in Article 83. Article 76(10) provides that the provisions of Article 76 are ‘without prejudice’ to the question of the delimitation of the continental shelf.51 ITLOS has indeed confirmed that ‘[t]here is a clear distinction between the delimitation of the continental shelf under article 83 and the delineation of its outer limits under article 76’.52 A coastal State could thus submit information to the CLCS regarding the establishment of outer limits of its continental shelf in areas where other States also assert rights to a continental shelf (within or beyond 200 M) as these overlapping entitlements would only subsequently be subject to delimitation. Unlike title to land, maritime entitlements are unique in that multiple States can have competing entitlements over the same area.53

However, the CLCS in its Rules of Procedure (RoP) has blurred the distinction between delineation and delimitation. The RoP includes a slight difference in terms of language concerning the relationship between delineation and delimitation. Rule 46(2) provides that the actions of the CLCS ‘shall not prejudice’ matters relating to the delimitation of boundaries between States.54 In other words, where Article 76(10) merely explained that Article 76 (and therefore delineation) does not prejudice delimitation, the RoP creates an obligation for the CLCS not to prejudice delimitation. The RoP thus stipulates that when there is a dispute in the delimitation of the continental shelf ‘or in other cases of unresolved land or maritime disputes’, submissions can be made and are to be considered by Annex 1 of the RoP.55 However, Annex I provides that the CLCS ‘shall not consider and qualify a submission’ made by any of the States concerned in a land or maritime dispute unless prior consent is given by all States to that dispute.56 This has meant that many submissions to the CLCS are prevented from being considered due to the existence of a dispute, a situation that ITLOS has called an ‘impasse’.57

Yet, according to a strict reading of Article 76, this did not need to happen. Why should it not be possible for the CLCS to make recommendations on the information submitted by the coastal State? The recommendations are simply that, recommendations, and – according to Article 76(10) – are without prejudice to delimitation.58 The limits of the continental shelf can only be final and binding if they are based on the recommendations of the CLCS as well as any potential outcome of delimitation processes. By not considering submissions from States that faced challenges from other States, the CLCS has inadvertently transformed what should have been a pure delineation exercise into a process that has already incorporated aspects typically reserved for the delimitation phase. This might be seen as a more realistic approach, but it has deviated from the original intent of maintaining a distinct delineation process.

Coastal States have used this approach when submitting information about their outer continental shelf to the CLCS. In its submission concerning the Norway Basin, for example, Norway acknowledged that its outer continental shelf is bound by the 200 M EEZ limits of Iceland and the Faroe Islands (Denmark).59 Similarly, in its submission on the northern region of the Faroe Islands, Denmark asserted that the outer boundaries of its continental shelf beyond the 200 M mark are defined by the 200 M limits set by Iceland, Jan Mayen (Norway), and the mainland of Norway.60 Furthermore, Indonesia, in its submission concerning the North Papua region, explicitly stated that the outer extents of its continental shelf beyond the 200 M threshold are restricted by the EEZ entitlements of Palau, Papua New Guinea, and the Federated States of Micronesia.61 Micronesia, Papua New Guinea, and the Solomon Islands in their joint submission also recognised that the outer limits of their continental shelves beyond 200 M are delineated by the 200 M EEZ limits of Nauru and Tuvalu.62 In limiting their entitlement to the outer continental shelf from encroaching on the 200 M limit of another State in their CLCS submissions, these States have inadvertently applied considerations of delimitation in a process that is supposed to be purely delineation.

Aside from submissions to the CLCS, this approach was also how most coastal States negotiated their continental shelf boundaries with each other. For instance, in the negotiation of its continental shelf boundary with Denmark on behalf of Greenland, Iceland acknowledged that its outer continental shelf entitlement is constrained by Greenland’s 200 M limit.63 When concluding their boundary agreement with Australia in 2004, New Zealand also agreed that its continental shelf beyond 200 M ends at the outer limits of the 200 M EEZ generated from Australia’s Lord Howe Island.64 Micronesia and Palau in their 2004 EEZ boundary agreement, whilst anticipating both Parties making future submissions to the CLCS, similarly agreed that neither one shall extend its outer continental shelf into the EEZ of the other.65 None of these boundary agreements provides any explanations on whether those constraints were applied after acknowledging that there are overlapping entitlements and that they agreed to delimit the boundaries on the 200 M limits; or if they recognised that an outer continental shelf entitlement may not overlap with the 200 M zone of another State. In any event, these practices further confuse the processes of delineation and delimitation.

In addition to State practice, this amalgamation of delineation and delimitation is likewise evident from the ITLOS Special Chamber’s judgment in the Mauritius/Maldives case. As already mentioned above, the Chamber in this case rejected Mauritius’ claim of natural prolongation because it goes through the Maldives continental shelf within 200 M.66 This shows that the Chamber imposed constraints on Mauritius’ entitlement within the delineation process even before advancing to the delimitation stage. The ICJ also holds this point of view in the Nicaragua v. Colombia case. If we apply the purist approach to delineation, Nicaragua and Mauritius should be allowed to establish the outer limits of their continental shelf beyond 200 M at any location, provided they adhere to the stipulations outlined in Article 7667 and are based on the recommendation of the CLCS. Nevertheless, the ICJ in its judgment has added another stipulation by asserting that Nicaragua’s entitlement to an outer continental shelf cannot extend within 200 M of Colombia’s baselines.68 By doing this, the ICJ has made a factor that should have been considered during a delimitation process a requirement in the delineation process. The recent case law has thus confused the relationship between delineation and delimitation altogether, as a coastal State’s delineation process now depends on the existence of other State’s entitlements.

The Practical Implications of the Recent Case Law

Beyond the confusion between delineation and delimitation, these recent judgments from ITLOS and the ICJ are likely to have significant impacts on how coastal States delineate and delimit their continental shelf moving forward. These implications will be discussed below.

New Constraint Line for a State’s Entitlement to an Outer Continental Shelf

According to Article 76, the legal concept of the continental shelf has two alternative limits: either it ends at 200 M from the baselines, or, it extends throughout the natural prolongation of the land territory to the outer edge of the continental margin.69 The outer edge of the continental margin can be delineated according to two scientific formulae: either by reference to the thickness of sedimentary rocks (the Gardiner formula) or by reference to a fixed distance from the foot of the continental slope (the Hedberg formula).70 Acknowledging that this method of delineating the continental shelf might allow certain coastal States to assert rights over vast areas of seabed, the participating States at the Third United Nations Conference on the Law of the Sea sought to protect the rights of the international community by implementing specific constraints on the continental shelf. Thus, two legal constraints were introduced: the limits of the outer continental shelf shall not exceed 350 M from the baselines or shall not exceed 100 M from the 2,500 metre isobath.71

The limits, formulae, and constraint lines are to be applied unilaterally by coastal States in identifying the extent of their continental shelf. They are based on the coastal States’ territory and their submerged prolongation. The recent ICJ decision on the outer continental shelf changes this significantly, for it implies that the extent of a coastal State’s (inherent) sovereign rights now also depends on the existence of (or lack thereof) another State’s EEZ and continental shelf (within 200 M) entitlements. Thus, in addition to the limits and constraint lines established by Article 76, a third constraint is added: the 200 M line from other States.

The constraint lines for the outer continental shelf have always been measured from the relevant coastal State’s baselines or 2,500-metre isobath, and not from another State’s baselines. Additionally, a coastal State has always been free to choose the constraint line that is more beneficial to it. However, this is not the case with the new constraint line measured from 200 M of another State. This means that this new constraint line would be more prominent than the other two provided under the LOS Convention.

The ICJ, unfortunately, did not elaborate on how coastal States should apply this third constraint line vis-à-vis the procedure before the CLCS. Under Article 76 of the LOS Convention, the coastal State should identify the limit of its outer continental shelf based on the Hedberg or Gardiner formula, wherever they are located, before applying the constraint lines of 350 M from the baselines or 100 M from the 2,500-metre isobath. In theory, the procedure should be the same for applying the new constraint line of 200 M from the baselines of another State. In other words, a coastal State should be able to delineate the outer edge of its continental margin and only afterwards apply the relevant constraint lines. However, the ITLOS Special Chamber’s decision in the Mauritius/Maldives case has thrown this process into question by stipulating that a route of natural prolongation that crosses another State’s ‘uncontested’ continental shelf is not legally valid.72 In other words, this new constraint line introduced by the recent case law is different from the pre-existing constraint lines in that it applies as a cut-off point before completing the delineation of the continental shelf.73

This decision implies that potential foot of the slope points within 200 M of other States may not be used, even if the eventual outer edge of the continental margin delineated from those points would be found just outside those 200 M limits. It would also mean that potential 2,500-metre isobaths within 200 M of other States may not be used, even if it means that the eventual constraint line (100 M from that isobath) may be determined just outside of those 200 M limits. These considerations are relevant in situations where a coastal State wants to delineate its outer continental shelf, but has several islands abutting the same continental margin. In these situations, it seems as if the coastal States submitting information to the CLCS may not include seabed features relevant to determining the outer edge of the continental margins if those features are located within 200 M of other States. If this is the case, then it would be impossible for some coastal States to prove the extent of their continental margin as they would be unable to identify the edge of the margin due to it being located within 200 M of another State.74

In principle, coastal States should be able to delineate their continental margin using the foot of the slope and/or sediment thickness formula, even if they are located within 200 M of another State. Only then should the constraint lines be introduced, including the 200 M limit from neighbouring States, to establish the extent of a State’s outer continental shelf. The ICJ should have clarified when this third constraint should be applied to prevent disputes and objections from arising when States submit their information to the CLCS, especially if there is a potential overlap with the 200 M entitlement of other States. In a broader context, the presence of a third constraint line introduces various questions, one of which pertains to how a coastal State’s continental shelf entitlement would now be influenced by the existence of another State’s 200 M entitlement.

Affirmation That There Is Not a ‘Single Continental Shelf’

The outcome of the recent case law means that the concept of a ‘single continental shelf’ is finally obsolete. Despite the differences between the continental shelf within and beyond 200 M discussed above, the concept of a ‘single continental shelf’ has been continuously upheld by courts and tribunals,75 as well as in scholarly literature.76 Although there is indeed one maritime zone that according to Article 77(3) is inherent in its entirety, the present authors do not believe the concept of a ‘single continental shelf’ to be helpful, since there are differences concerning delineation and the substantive rights.77

The concept of a ‘single continental shelf’ was indeed an accurate way to describe the shelf regime when the term ‘continental shelf’ was still largely based on the geomorphological definition of the term.78 However, after the adoption of the LOS Convention, which provides different bases of entitlement to the continental shelf within and beyond 200 M, there are clear differences between the inner and outer continental shelf. For the inner continental shelf, distance determines the extent of the entitlement.79 On the other hand, distance does not play a part in determining entitlement to the outer continental shelf, with geomorphology and geology being the relevant factors.80

Even though the ICJ and the ITLOS Special Chamber recalled the concept of a ‘single continental shelf’ in their judgments,81 the fact that the Court established a new constraint line to limit coastal States’ entitlement to an outer continental shelf adds another difference between the inner and the outer continental shelf. According to the ICJ, an outer continental shelf entitlement of one State may not overlap with an inner continental shelf entitlement of another, but it may overlap with an outer continental shelf entitlement of that other State. The Court further mentioned that ‘the basis for the entitlement to a continental shelf within 200 nautical miles from a State’s baselines differs from the basis for entitlement beyond 200 nautical miles’,82 which seems to be an acknowledgment of the specific differences between the inner and outer continental shelf.83 In other words, the recent decisions indicate that it may now be time to let go of the concept of a ‘single continental shelf’, and instead assess each delineation and delimitation in light of its own circumstances.

Is There Still a Need for Grey Areas in Maritime Delimitations?

The decision of the ICJ not to allow Nicaragua’s outer continental shelf to overlap with the 200 M entitlement of Colombia contradicts the decisions of ITLOS and an ad hoc tribunal in the Bay of Bengal cases.84 In the latter, due to the geographical positions of the disputing parties, the maritime boundaries established by both tribunals have delimited areas that extend beyond 200 M from the coastline of Bangladesh but fall within 200 M from the coasts of Myanmar and India, referred to as the ‘grey areas’.85 The creation of grey areas thus implies that such competing claims to entitlement may exist.86 The tribunal in the Bangladesh v. India case emphasised that beyond 200 M from its coast, Bangladesh had no entitlement to an EEZ which would otherwise have conferred sovereign rights to the living resources of the water column in addition to the resources of the seabed and subsoil. Instead, Bangladesh only had an entitlement to the seabed and its subsoil under the legal regime governing the continental shelf.87 Both tribunals in this case ruled that Bangladesh’s entitlement over the continental shelf beyond 200 M can indeed extend into the EEZ entitlements of Myanmar and India, thus giving rise to the grey areas.

The ICJ alluded to the ‘possibility’ of a grey area in its 2021 decision on the Somalia v. Kenya case but did not go further to elaborate on the legal regime that would be applicable in such an area.88 However, the Court distinguished the Nicaragua v. Colombia case from the previous cases and ignored its own considerations in Somalia v. Kenya as well as those of the tribunals in the Bay of Bengal cases.89 If we follow the precedent set by the ICJ in the Nicaragua v. Colombia case, there would not be any grey areas between Bangladesh, Myanmar, and India, as Bangladesh would not be able to have a continental shelf entitlement within 200 M from the baselines of Myanmar and India.90 Although it should be noted that the judgment between Nicaragua and Colombia is only binding between those two parties and does not enjoy direct application in the Bay of Bengal, the judgment raises various issues concerning the necessity and validity of past and potential future grey areas. The Bay of Bengal cases involved coastal States that are adjacent to each other and situated on a convex coast, which unfairly limited the continental shelf projection of Bangladesh. By creating the grey areas, the tribunals addressed this by adjusting the boundary lines as such to allow Bangladesh to have an outer continental shelf. This would not be possible if a strict application of the new constraint line was used. However, it is not clear whether this constraint line set by the ICJ (and thus a rejection of grey areas) only applies to coastal States with opposite coasts, such as in the case between Nicaragua and Colombia, or if it applies in general in any coastal geography, including coastal States with adjacent coasts.91

Solving the Question of the Applicable Delimitation Methodology beyond 200 M?

A final implication of the recent case law is that there is no longer a need to discuss what kind of delimitation methodology is applicable and appropriate to delimit an outer continental shelf entitlement overlapping with an inner continental shelf entitlement. Previously, there were debates on whether in these situations distance took precedence over geological and/or geomorphological criteria in the delimitation of those overlapping entitlements.92 Where the ICJ in the North Sea Continental Shelf Cases emphasised the importance of natural prolongation and the sense of something already possessed,93 subsequent case law has abandoned that part of the legal concept of the continental shelf, at least within 200 M, after the establishment of the EEZ.

In situations where only entitlements within 200 M were delimited, distance and adjacency have been the most important (if not the only) factors in determining entitlements and subsequent delimitation. In such a case, scientific criteria, ‘natural prolongation’, or any potential outer continental shelf entitlement have generally not been considered.94 The debate remained, however, on how to delimit an outer continental shelf of a State with another State’s 200 M entitlements. This issue is seemingly settled with the ICJ’s judgment in Nicaragua v. Colombia, where the ICJ stated that such a situation can no longer exist. In an area where one State has an inner continental shelf entitlement up to 200 M and another State would have otherwise had an entitlement to an outer continental shelf, no such outer continental shelf entitlement exists, thus leaving ‘no area of overlapping entitlement to be delimited’.95 This means that in these situations, there is no longer a need to discuss whether the three-stage approach, with its reliance upon the equidistance/median line, is appropriate in those situations.96

Conclusion

The ICJ’s decision in the delimitation of the continental shelf between Nicaragua and Colombia had the potential to be a seminal turning point in the development of the regime of the continental shelf. It is unfortunate, however, that the Court did not elaborate on the thinking and legal considerations behind its finding. Through this ruling, the ICJ seemed to try to preserve what the Court perceived as the intention of the drafters of the LOS Convention in establishing the 200 M entitlements of the EEZ and continental shelf for coastal States. Furthermore, not allowing the outer continental shelf of one State to encroach into the 200 M of another State will resolve some of the outstanding submissions that are under consideration by the CLCS. However, it would have been more helpful if the Court expressly addressed all these points in its decision and elaborated upon them. It also remains unclear why these issues were not discussed in 2012 or 2016, thus giving the impression that the ICJ has reversed its position compared to previous judgments between these two parties.97 Though the dissenting opinions raise valid and important concerns about the majority decision, it is a shame that the judgment does not attempt to address these, for it would have substantiated and clarified the ICJ’s official position.

The approach of the ICJ and the ITLOS Special Chamber significantly confuse the objective of delineation. One could not help but wonder if the better approach was for the ICJ to allow Nicaragua’s outer continental shelf entitlement to overlap with Colombia’s 200 M provided that the conditions of Article 76 were met. The Court could have drawn attention to the fact that under the LOS Convention, neither the EEZ nor the continental shelf regime occupies a privileged position for maritime delimitation. The Court could have asserted that, while for Colombia distance is the primary consideration for delimitation (due to the overlapping area between the two States being within 200 M from their coasts), for Nicaragua geomorphology and geology are the main factors for delimitation (since the overlapping area is beyond 200 M from the coasts of the two States). By allowing the different entitlements to overlap, the ICJ would then have had to delimit the overlapping area between the two countries.98

If the Court did not favour the idea of creating a grey area as in the Bay of Bengal cases, the ICJ could instead have drawn the boundary at the outer limit of Colombia’s 200 M zone.99 Using the three-stage method of delimitation favoured by the ICJ, the Court would have had a lot of flexibility in adjusting the equidistance line in the second and third stages. The ICJ could have considered the distance factor in the second stage and adjusted the boundary to coincide with the outer limit of Colombia’s EEZ. The Court could have also decided in the third stage that the provisional equidistance line is disproportionate considering the coastal length of both parties and the relevant disputed area and that drawing the boundary at the outer limit of Colombia’s 200 M zone eliminates this disproportionality.100 Alternatively, the Court could have decided that in this particular case, the three-stage method of delimitation was inappropriate, and could have determined that any Nicaraguan entitlement to a continental shelf within 200 M of Colombia would not be given effect in the delimitation process.101

Ultimately, the recent case law on the delimitation of the continental shelf has given rise to more questions than answers. It remains unclear what the legal basis is for concluding that an outer continental shelf entitlement may not extend within 200 M of another State, not to mention the shaky grounds upon which that rule of customary international law has been found. Furthermore, the conclusions of both the ICJ and ITLOS have confused the relationship between delineation and delimitation and have incorporated considerations of the latter into the former. These conclusions have practical implications for both delineation and delimitation of the outer continental shelf, as they essentially create a new constraint to the entitlement of a continental shelf beyond 200 M, one which cannot explicitly be found in either Article 76 or Article 83, or any other provision in the Convention for that matter. We will have to wait and see what the international response is to the recent case law, and whether it will change States’ approach to delineation and delimitation of the continental shelf

1

As of 29 November 2023, there have been 93 submissions to the Commission on the Limits of the Continental Shelf [CLCS] to delineate the outer limit of their continental shelves beyond 200 M. See Submissions, through the Secretary-General of the United Nations, to the Commission on the Limits of the Continental Shelf, pursuant to article 76, paragraph 8, of the United Nations Convention on the Law of the Sea of 10 December 1982, https://www.un.org/depts/los/clcs_new/commission_submissions.htm. All websites accessed on 29 November 2023, unless otherwise mentioned.

2

United Nations Convention on the Law of the Sea (Montego Bay, 10 December 1982, in force 16 November 1994) 1833 UNTS 3 [LOS Convention].

3

Ibid., Article 76(5).

4

The term ‘outer continental shelf’ (or ‘extended continental shelf’) is not a legal term used in the LOS Convention. Even so, it has been widely adopted when referring to the continental shelf beyond 200 M. The authors prefer to use the term ‘outer continental shelf’ since the continental shelf is not itself being extended; see Arbitration between Barbados and the Republic of Trinidad and Tobago, Award, 11 April 2006, (2006) 27 RIAA 147, at footnote 4 [Barbados v. Trinidad & Tobago].

5

LOS Convention (n 2), Articles 76(4), 76(8).

6

Question of the Delimitation of the Continental Shelf Between Nicaragua and Colombia Beyond 200 Nautical Miles from the Nicaraguan Coast (Nicaragua v. Colombia), ICJ, Judgment, 13 July 2023 [Nicaragua v. Colombia]; Dispute concerning Delimitation of the Maritime Boundary between Mauritius and Maldives in the Indian Ocean (Mauritius/Maldives), Judgment, 28 April 2023, ITLOS Case No. 28 [Mauritius/Maldives].

7

Mauritius/Maldives (n 6), para 57.

8

Ibid., para 274.

9

Ibid., para 434.

10

Ibid., para 444.

11

Ibid (emphasis added).

12

Territorial and Maritime Dispute (Nicaragua v. Colombia), Judgment, 19 November 2012, ICJ Reports 2012, p. 624, para 113.

13

Ibid., para 114.

14

Question of the Delimitation of the Continental Shelf between Nicaragua and Colombia beyond 200 Nautical Miles from the Nicaraguan Coast (Nicaragua v. Colombia), Preliminary Objections, 17 March 2016, para 84.

15

LOS Convention (n 2), Article 76(8) and Annex II, Article 4.

16

Nicaragua v. Colombia, Preliminary Objections (n 14), para 105 (emphasis added).

17

Ibid., para 107.

18

Ibid., para 110.

19

Ibid., para 114.

20

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, p. 563.

21

Nicaragua v. Colombia, Judgment (n 6), para 79.

22

Ibid., para 82.

23

Ibid., paras 86 & 91.

24

See, e.g., H 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!, 21 July 2023) available 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/; O Pomson, ‘The ICJ’s 2023 judgment in Nicaragua v Colombia: A new chapter in the identification of customary international law?’ (CIL Blog, 28 July 2023) available at https://cil.nus.edu.sg/blogs/the-icjs-2023-judgment-in-nicaragua-v-colombia-a-new-chapter-in-the-identification-of-customary-international-law/; V De Lucia, ‘On the Question of Opino Juris in Nicaragua vs. Colombia (Judgement 13 July 2023)’ (EJIL:Talk!, 3 August 2023) available at https://www.ejiltalk.org/on-the-question-of-opinio-juris-in-nicaragua-vs-colombia-judgement-13-july-2023/; MD Evans and NA Ioannides, ‘A commentary on the 2023 Nicaragua v Colombia Case’ (EJIL: Talk!, 4 August 2023) available at https://www.ejiltalk.org/a-commentary-on-the-2023-nicaragua-v-colombia-case/.

25

Judge Tomka, Judge Robinson, Judge Charlesworth and Judge ad hoc Skotnikov have each appended a dissenting opinion to the judgment.

26

Nicaragua v. Colombia (n 6), para 77.

27

It is interesting that the ICJ did not refer to the practice of States in concluding maritime boundary agreements for continental shelves beyond 200 M, see L Bernard and C Schofield, ‘Disputes concerning the delimitation of the continental shelf beyond 200 nautical miles’ in T Heidar (ed), New Knowledge and Changing Circumstances in the Law of the Sea (Brill Nijhoff, Leiden, 2020) 157–182, Table 8.1.

28

Woker (n 24). For example, Colombia submitted that the joint submission by Costa Rica and Ecuador in 2020 ‘clearly reflected the opinio juris’. However, Holly Leung categorises this example as one of ‘comity’ rather than ‘clear opinio juris’. See the Verbatim Record of Friday, 9 December 2022, in the case concerning the Question of the Delimitation of the Continental Shelf between Nicaragua and Colombia beyond 200 Nautical Miles from the Nicaraguan Coast (Nicaragua v. Colombia) 22–23; H Leung, ‘The extended continental shelf in Nicaragua v Colombia: Identifying a customary rule based on CLCS submissions?’ 11th ABLOS Conference (Monaco, 11–12 October 2023). Note, however, Judge Iwasawa’s separate opinion, where he argued that ‘States usually do not curtail themselves when they believe that they have a right’, and how this ‘sense of legal obligation has been expressly indicated by some States that have refrained from extending an outer continental shelf within 200 nautical miles of the baselines of another State’, see Nicaragua v. Colombia, Separate Opinion of Judge Iwasawa, paras 12–14.

29

Nicaragua v. Colombia, Order of 4 October 2022 (n 20); Mauritius/Maldives (n 6), para 57.

30

Nicaragua v. Colombia, Judgment (n 6), para 82 (emphasis added).

31

Mauritius/Maldives (n 6), para 444 (emphasis added).

32

Article 77(3) of the LOS Convention (n 2) provides that the rights over the continental shelf do not depend on any express proclamation.

33

These differences become clear through Articles 76(1), 82, and 246(6) of the LOS Convention (n 2).

34

Barbados v. Trinidad & Tobago (n 4), para 213.

35

See L Bernard, ‘The problem with the concept of single continental shelf’ (2022) 7(1) Asia-Pacific Journal of Ocean Law and Policy 91–109; H Woker, ‘Challenging the notion of a single continental shelf’ (2023) 54(4) Ocean Development & International Law 375–392, doi: 10.1080/00908320.2023.2271393.

36

See, e.g., Continental Shelf (Tunisia/Libyan Arab Jamahiriya), Dissenting Opinion of Judge Shigeru Oda, ICJ Reports 1982, p. 100, para 233; D Attard, The Exclusive Economic Zone in International Law (Clarendon Press, Oxford, 1987) 212; FO Vicuńa, The Exclusive Economic Zone: Regime and Legal Nature under International Law (Cambridge University Press, Cambridge, 1989) 69; MD Evans, ‘Delimitation and the common maritime boundary’ (1994) 64(1) British Yearbook of International Law 282–332, at pp. 286–293.

37

Continental Shelf (Libyan Arab Jamahiriya/Malta), Merits, Judgment, 3 June 1985, ICJ Reports 1985, p. 13 [Libya/Malta], para 33; Barbados v. Trinidad & Tobago (n 4), para 234; see also Vicuńa (n 36).

38

A Proelss, ‘Article 56: Rights, jurisdiction and duties of the coastal State in the exclusive economic zone’ in A Proelss (ed), United Nations Conventions on the Law of the Sea: A Commentary (CH Beck, Munich, 2017) 418–436, at p. 436.

39

Attard (n 36), at p. 132.

40

LOS Convention (n 2), Article 56(3); Libya/Malta (n 37).

41

Libya/Malta (n 37), para 34.

42

Ibid., para 39.

43

P Weil, The Law of Maritime Delimitation – Reflections (Grotius Publications Limited, Cambridge, 1989) 38.

44

Colson stated that for a continental shelf within 200 M, ‘[n]atural prolongation in a physical sense, for all practical purposes, was dead’. DA Colson, ‘The delimitation of the outer continental shelf between neighboring States notes and comments’ (2003) 97 American Journal of International Law 91, at p. 101. See also K Highet, ‘The use of geophysical factors in the delimitation of maritime boundaries’ (1993) 1 International Maritime Boundaries 176, who notes that ‘[i]t was the Libya/Malta case that finally disposed of “natural prolongation” once and for all – at least up to a distance of 200 n.m. from the baseline’. He also noted that in Libya/Malta, the ICJ ‘delivered a mortal blow’ to natural prolongation, ibid., at p. 179; See also J Lilje-Jensen and M Thamsborg, ‘The role of natural prolongation in relation to shelf delimitation beyond 200 nautical miles’ (1995) 64 Nordic Journal of International Law 619, at pp. 621–622, providing that Libya/Malta marked the ‘final breach’ of the rule of entitlement based on physical natural prolongation.

45

Barbados v. Trinidad & Tobago (n 4), para 225.

46

Nicaragua v. Colombia (n 6), para 78.

47

Ibid., para 70.

48

Although the ITLOS Special Chamber in Mauritius/Maldives did not go so far as to conclude this specifically, the fact that they referred to an ‘uncontested’ continental shelf implies that it may support such a conclusion implicitly.

49

Nicaragua v. Colombia (n 6), Dissenting Opinion of Judge Robinson, para 1.

50

Ibid., Dissenting Opinion of Judge Charlesworth, para 3.

51

This point was also argued by Nicaragua in the second round of oral pleadings. Verbatim Record of Wednesday, 7 December 2022, in the case concerning the Question of the Delimitation of the Continental Shelf between Nicaragua and Colombia beyond 200 Nautical Miles From the Nicaraguan Coast (Nicaragua v. Colombia) 14–21.

52

Dispute Concerning Delimitation of the Maritime Boundary Between Bangladesh and Myanmar in the Bay of Bengal (Bangladesh/Myanmar), ITLOS, Judgment, 14 March 2012, ITLOS Reports 2012, para 376 [Bangladesh/Myanmar].

53

Nicaragua v. Colombia (n 6), Dissenting Opinion of Judge Tomka, para 12. See also Nicaragua v. Colombia, Dissenting Opinion of Judge Robinson, para 5, who refers to this as the ‘co-equality of maritime zones’.

54

Rules of Procedure of the Commission on the Limits of the Continental Shelf, UN Doc CLCS/40/Rev.1 (17 April 2008), Rule 46(2).

55

Ibid., Rule 46(1).

56

Ibid., Annex I.

57

Bangladesh/Myanmar (n 52), paras 390–392.

58

The counterargument is that Article 76(8) provides that the limits of the continental shelf established by the coastal State ‘on the basis of’ the CLCS’ recommendations are ‘final and binding’, thus raising the question of how those final and binding limits would be affected by any delimitation process.

59

Continental Shelf Submission of Norway in Respect of Areas in the Arctic Ocean, the Barents Sea and the Norwegian Sea, (2006) available at http://www.un.org/depts/los/clcs_new/submissions_files/nor06/nor_exec_sum.pdf. See also the Verbatim Record of Tuesday, 6 December 2022, in the case concerning the Question of the Delimitation of the Continental Shelf between Nicaragua and Colombia beyond 200 Nautical Miles from the Nicaraguan Coast (Nicaragua v. Colombia) 39–40.

60

Partial Submission of the Government of the Kingdom of Denmark together with the Government of the Faroes to the Commission on the Limits of the Continental Shelf: The Continental Shelf North of the Faroe Islands (2009) available at http://www.un.org/depts/los/clcs_new/submissions_files/dnk28_09/dnk2009executivesummary.pdf. See also the Verbatim Record of 6 December 2022 (n 59), at p. 40.

61

See Continental Shelf Submission of the Republic of Indonesia: Partial Submission with Respect to the Area of North of Papua (2018) available at https://www.un.org/Depts/los/clcs_new/submissions_files/idn1_83_19/2019-02-01_IDN-Executive_Summary.pdf.

62

Joint Submission to the Commission on the Limits of the Continental Shelf concerning the Ontong Java Plateau by the Federated States of Micronesia, Papua New Guinea and the Solomon Islands (2009) available at http://www.un.org/depts/los/clcs_new/submissions_files/fmpgsb32_09/exsumdocs/fmpgsb2009executivesummary.pdf. See also the Verbatim Record of 6 December 2022 (n 59), at p. 37.

63

BM Magnússon, ‘Denmark (Greenland)-Iceland, Report 9-22 (2)’ in C Lathrop (ed), International Maritime Boundaries, Vol. VII (Brill Nijhoff, Leiden, 2016) 5259–5273, at p. 5268.

64

The Treaty between the Government of Australia and the Government of New Zealand establishing certain Exclusive Economic Zone and Continental Shelf Boundaries (25 July 2004).

65

Treaty between the Federated States of Micronesia and the Republic of Palau Concerning Maritime Boundaries and Cooperation on Related Matters (5 July 2006) Article 3.

66

Mauritius/Maldives (n 6), para 444. Mauritius proposed another two routes of natural prolongation not going through 200 M of the Maldives, but the Chamber determined that it could not establish the continental shelf boundary beyond 200 M between Mauritius and the Maldives due to uncertainties surrounding Mauritius’ grounds for natural prolongation. Ibid., para 449.

67

These requirements include the cut-off limits of 350 M from the baselines or 100 M from the 2,500-metre isobaths. See LOSC (n 2), Article 76(5).

68

Nicaragua v. Colombia (n 6), para 79.

69

LOS Convention (n 2), Article 76(1).

70

Ibid., Article 76(4).

71

Ibid., Article 76(5). In the case of submarine elevations and ridges, special considerations apply. See LOS Convention (n 2), Article 76(6). See, e.g., KA Baumert and L Mayer, ‘Submarine ridges and submarine elevations under the Law of the Sea Convention: A further look’ in T Heidar (ed) (n 27). The Statement of Understanding of the Bay of Bengal (SoU BoB) included in Annex II to the Final Act of UNCLOS III complicates this a little further by recognising a third alternative for determining the outer edge of the continental margin, namely, at the point where ‘the thickness of sedimentary rock is not less than 1 kilometre’. See Final Act of the Third United Nations Conference on the Law of the Sea, UN Doc A/CONF.62/121 (27 October 1982), Annex II. However, at no point does the Convention or the SoU BoB establish that the delineation of the outer continental shelf is dependent upon the presence of other States’ entitlements.

72

Mauritius/Maldives (n 6), para 444.

73

As Nicaragua had argued, ‘[t]o ask the Court to write that constraint into Article 76 is asking the Court to legislate in a way with which the many State Parties of [the LOS Convention] did not agree’. Comments by Nicaragua to Colombia’s Reply to Judge Robinson’s Questions (on file with the authors), para 26.

74

Judge Robinson goes so far as to argue that the ICJ’s judgment ‘has denied a coastal State the full benefit of the natural prolongation criterion in Article 76(1) of the Convention, which reflects customary international law’. Nicaragua v. Colombia (n 6), Dissenting Opinion of Judge Robinson, para 2.

75

Barbados v. Trinidad and Tobago (n 4); Bangladesh/Myanmar (n 52); In the matter of the Bay of Bengal Maritime Boundary Arbitration, The People’s Republic of Bangladesh and the Republic of India, Award, 7 July 2014, PCA Case No. 2010–16 [Bangladesh v. India]; Dispute Concerning Delimitation of the Maritime Boundary between Ghana and Côte d’Ivoire in the Atlantic Ocean (Ghana/Côte d’Ivoire), Judgment, 23 September 2017, ITLOS Reports 2017, p. 4.

76

B Kunoy, ‘Agreed minutes on the delimitation of the continental shelf beyond 200 nautical miles between Greenland and Iceland in the Irminger Sea’ (2013) 12 Chinese Journal of International Law 125, at p. 137; BM Magnússon, The Continental Shelf Beyond 200 Nautical Miles: Delineation, Delimitation and Dispute Settlement (Koninklijke Brill NV, Leiden, 2015) 136; X Liao, ‘Is there a hierarchical relationship between natural prolongation and distance in the continental shelf delimitation?’ (2017) 32 International Journal of Marine and Coastal Law 1–37, at p. 7.

77

For the present authors’ views on this issue, see Bernard (n 35); Woker (n 35).

78

Convention on the Continental Shelf (Geneva, 29 April 1958, in force 10 June 1964) 499 UNTS 311, Article 1.

79

Libya/Malta (n 37), para 61; Separate Opinion of Judge Iwasawa (n 28), para 4.

80

Note, however, that the distance factor still plays a role in providing a ‘cut-off’ to the outer continental shelf. See LOS Convention (n 2), Article 76(5).

81

Mauritius/Maldives (n 6), para 274; Nicaragua v. Colombia (n 6), para 75.

82

Nicaragua v. Colombia (n 6), para 75.

83

Judge Bhandari also pointed out that when the Court asserted that the substantive rights of a coastal State regarding its continental shelf are ‘generally the same’ both within and beyond 200 M, the Court was ‘diluting the notion of a single continental shelf’. Nicaragua v. Colombia (n 6), Declaration of Judge Bhandari, para 5.

84

Nicaragua v. Colombia (n 6), Dissenting Opinion of Judge Tomka, para 31; Dissenting Opinion of Judge ad hoc Skotnikov, para 17.

85

Bangladesh v. India (n 75), para 498.

86

Bangladesh/Myanmar (n 52); Bangladesh v. India (n 75).

87

Bangladesh v. India (n 75), para 503.

88

Maritime Delimitation in the Indian Ocean (Somalia v. Kenya), Judgment, 12 October 2021, ICJ Reports 2021, para 197.

89

Nicaragua v. Colombia (n 6), para 72.

90

Ibid., Dissenting Opinion of Judge Charlesworth, para 22.

91

See ibid., Dissenting Opinion of Judge Tomka, para 36.

92

Liao (n 76); Magnússon 2015 (n 76), at pp. 142–143.

93

North Sea Continental Shelf Cases (Federal Republic of Germany/Denmark; Federal Republic of Germany/Netherlands), ICJ, Judgment, 20 February 1969, ICJ Reports 1969, para 19.

94

In the Gulf of Maine case, for example, a chamber of the ICJ determined that ‘adjacency’ may better express the link between a State’s sovereignty and sovereign rights over adjacent submerged land, rather than ‘natural prolongation’. However, it also recognised that adjacency alone does not produce a legal title. See Case Concerning Delimitation of the Maritime Boundary in the Gulf of Maine Area (Canada/United States of America), ICJ, Judgment, 12 October 1984, ICJ Reports 1984, para 103.

95

Nicaragua v. Colombia (n 6), para 86.

96

Several scholars have raised concerns about the three-stage approach’s applicability to the continental shelf’s delimitation beyond 200 M. See, e.g., Woker (n 35); Liao (n 76); T Davenport, ‘The China-Japan Dispute over entitlement in the East China Sea: Legal issues and prospects for resolution’, in CH Schofield, S Lee and M-S Kwon (eds), The Limits of Maritime Jurisdiction (Brill Nijhoff, Leiden, 2013) 320; J Gao, ‘The Okinawa Trough issue in the continental shelf delimitation disputes within the East China Sea’ (2010) 9 Chinese Journal of International Law 143, at pp. 169–177. However, those discussions will continue to exist with regard to the delimitation of two or more outer continental shelf entitlements.

97

This question was also raised in Nicaragua v. Colombia (n 6), Dissenting Opinion of Judge Tomka, paras 4–6.

98

Indeed, as Judge Tomka submits, ‘[s]hould the Parties’ entitlements overlap, it would be for the Court to adopt its own equitable solution’. Ibid., para 19.

99

See also Nicaragua v. Colombia, Dissenting Opinion of Judge Charlesworth, para 33. Colombia has submitted that the ICJ would first need to determine whether Nicaragua’s entitlement extended thus far, which it submits would not be possible without CLCS recommendations. See Verbatim Record of Friday, 8 December 2022, in the case concerning the Question of the Delimitation of the Continental Shelf between Nicaragua and Colombia beyond 200 Nautical Miles from the Nicaraguan Coast (Nicaragua v. Colombia) 11–12. However, the ICJ could have phrased its conclusion in such a way as to make it dependent upon such CLCS recommendations if it so wished.

100

According to Jagota, the concept of ‘proportionality’, ‘while not applicable to geological and juridical appurtenance of the continental shelf, may properly be used as a criterion to evaluate the effect of geographical features on a delimitation in marginal areas’. See SP Jagota, Maritime Boundaries (Martinus Nijhoff Publishers, Dordrecht, 1985) 175. It was recognised by Nicaragua in the oral pleadings that there could have been alternatives to simply drawing a median line between the two outer limits, as long as the delimitation produced an equitable solution. See Verbatim Record of Monday, 5 December 2022, in the case concerning the Question of the Delimitation of the Continental Shelf between Nicaragua and Colombia beyond 200 Nautical Miles from the Nicaraguan Coast (Nicaragua v. Colombia) 29.

101

In Territorial and Maritime Dispute (Nicaragua v. Colombia), the ICJ accepted that an entitlement to a continental shelf or EEZ may overlap with the territorial sea of another State, but that the continental shelf entitlement in this case would not be given effect, which is different from concluding that the entitlement did not exist in the first place. Territorial and Maritime Dispute (n 12), para 177. See also Nicaragua v. Colombia (n 6), Dissenting Opinion of Judge Charlesworth, para 9.

Figure 1

Image reproduced from the counter-memorial of the Maldives depicting one of the routes of natural prolongation relied upon by Mauritius, traversing through the 200-M zone of the Maldives (Dispute concerning delimitation of the maritime boundary between Mauritius and Maldives in the Indian Ocean (Mauritius/Maldives), ITLOS, Counter-memorial of Maldives, Figure 9, at p. 43)
Figure 2

Image reproduced from the 2023 ICJ judgment depicting Colombia’s 200-M zone, and Nicaragua’s asserted outer limits of its continental shelf within that zone (Question of the Delimitation of the Continental Shelf Between Nicaragua and Colombia Beyond 200 Nautical Miles from the Nicaraguan Coast (Nicaragua v. Colombia), ICJ, Judgment, 13 July 2023, at p. 18)