The Recognition of a Customary Rule of International Law in NICOL II – A Redundant Exercise?

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In Question of the Delimitation of the Continental Shelf between Nicaragua and Colombia beyond 200 Nautical Miles from the Nicaraguan Coast (NICOL II), the International Court of Justice (ICJ) observed a general trend in which coastal States had “chosen not to assert” outer continental shelf entitlement “within 200 nautical miles of the baselines of another State” (para 77). The respondent argued that in 51 submissions of States, under Article 76 of UNCLOS, the proposed outer limits “stopped at the 200-nautical-mile zones of other States when, on technical grounds [..] they could have gone further”. The Court held that this practice reflected a rule of customary international law.

The above determination has triggered criticism as to whether the practice identified by the Court as the basis for a rule of customary international law was accompanied by opinio juris. Judge Tomka noted in his dissenting opinion that the analysis of the ICJ “is incomplete” (para 44) for a number of reasons, including the lack of analysis of “the existence of contrary State practice” (para 45). Judge Xue (para 47) and Judge Robinson (para 19) expressed, in their respective dissenting opinions, similar reservations to the findings of the ICJ concerning the existence of a customary rule of international law.

This post will not address these concerns. Rather, this post will examine the question whether it was necessary for the ICJ to undertake the analysis required to determine the existence of a customary rule of international law. It will be concluded that existing international law does not allow outer continental shelf entitlements to extend into areas landward the 200 M distance line of States with an opposite coast. Accordingly, there was no need for the ICJ in NICOL II to undertake the arduous analysis to seek the identification of a customary rule of international law.

Case Law

It is difficult to accept the proposition that the conclusion of the ICJ in its judgment on preliminary objections in NICOL II cannot but be read to mean that the applicant, in the fulfilment of its obligation in Article 76(8) of UNCLOS, had, to rely on the expression from the judgment on merits in NICOL, “established that it ha[d] a continental margin that extends far enough to overlap with Colombia’s 200 [M] entitlement to the continental shelf” (para 129). It is for these reasons that the ICJ in the judgment on preliminary objections in NICOL II held that the submission of Nicaragua to delimit the putative overlap was “admissible” (para 115). Consequently, the claim being admissible would render it difficult to accept the proposition that the claimed entitlement of Nicaragua would not be possible under international law. From this basis it may appear obscure that the ICJ in the judgment on merits in NICOL II for reasons explained above refused to accept the final submission of the Applicant. This is by analogy illustrated in Tunisia/Libya, where the ICJ observed that “[t]he need for delimitation of areas of continental shelf between the Parties can only arise within the submarine region in which claims by them to the exercise of sovereign rights are legally possible according to international law” (para 34). A fortiori, accepting to uphold the submission of the applicant in its decision on preliminary objections in NICOL II, cannot be read otherwise than to mean that the claim of Nicaragua consistent with which its entitlement extends into the 200 M zone of Colombia is, to rely on the expression in Tunisia/Libya, ´legally possible`.

Interestingly, it would appear that the critical question discussed in NICOL II whether a claimed outer continental shelf entitlement from Nicaragua may extend into the area landward the 200 M distance line of mainland Colombia had been touched on by the arbitral tribunal in the Bay of Bengal Maritime Arbitration with an outcome that is different from the conclusion in NICOL II. According to the arbitral tribunal, upon stressing the importance of the concept of a single continental shelf in international law, it observed that “the coast is relevant, irrespective of whether that overlap occurs within 200 nm of both coasts, beyond 200 nm of both coasts, or within 200 nm of one and beyond 200 nm of the other” (para 299) [emphasis added]. The conjunction ´and` confirms that it follows from the reasoning of the arbitral tribunal that an overlap similar to the matter under review in NICOL II could arise and would be permissible. While the observation of the arbitral tribunal must be seen as an obiter dictum it must still be seen to reflect the view of the five arbitrators sitting on the bench in the Bay of Bengal Maritime Arbitration. To the best knowledge of the author of this blog, the parties in NICOL II did not rely on the above statement made by the arbitral tribunal in the Bay of Bengal Maritime Arbitration.

The Delimitation Methodology

It is recalled that in its final submission I(3) in NICOL, Nicaragua requested the Court to define “a continental shelf boundary dividing by equal parts the overlapping entitlements to a continental shelf of both Parties” (para 106). In the second round of oral argument, Nicaragua suggested that “the Court could make that delimitation by defining the boundary in words such as ‘the boundary is the median line between the outer edge of Nicaragua’s continental shelf fixed in accordance with UNCLOS Article 76 and the outer limit of Colombia’s 200-mile zone´”. The applicant argued that this formula “does not require the Court to determine precisely where the outer edge of Nicaragua’s shelf lies. The outer limits could be then established by Nicaragua at a later stage, on the basis of the recommendations of the [CLCS]” (para 128).

The submission of the applicant resulted in two challenges. First, the reason for which the formula in question is put forward, rather than requesting the ICJ to draw a provisional equidistance line, measured from relevant basepoints, applicable under the first step in the “delimitation methodology” (paras 115 – 122) is likely due to the point of fact that in any similar situation, where a claimed overlap of  entitlements between two States with opposite coasts, a median line will necessarily be located beyond the area of claimed overlap (p. 368). This would constitute an absurd point of departure for applying the first step under the delimitation methodology, which is quasi compulsory in the absence of compelling reasons (para 116) to the contrary, but in which case the delimitation methodology, which relies on micro geography, is replaced by a method that relies on macro geography and which in any case would not have a different result. Second, it is beyond any question that in order to uphold the final submission of the applicant and establish a delimitation line that depends upon and is partly generated from the seaward limits of the putative entitlement of the applicant, would necessarily imply that the delimitation would rely on geomorphological criteria. This would appear difficult to be accommodated in the Libya / Malta (para 40), which can be seen a capital punishment in so far concerns whether natural prolongation is to be given any role in a delimitation. Only factors relating to the coastal configuration are objective and therefore equitable for the purpose of the delimitation operation.

The trend in the case law consistent with which only projections from the coastal configuration have been deemed objective has also been transposed to disputes with overlapping outer continental shelf entitlements as is illustrated in the Ghana/Côte d´Ivoire case (para 526). However, the case law dismissing the role of geomorphology in delimitations, where there are overlapping outer continental shelf entitlements, relates exclusively to disputes between States with adjacent coasts. Does this matter? It is true that the delimitation methodology regarding overlapping entitlements of areas within 200 M from the baselines of all the involved States does not differentiate between situations where the coasts are opposite or adjacent (para 116). Yet, it may be argued that the rationale for dismissing any role to geomorphology in outer continental shelf disputes between States with adjacent coasts need not necessarily be transposed to outer continental shelf disputes between States with opposite coasts. It is recalled that the basis of the entitlement to outer continental shelf rests on geomorphology and geology (para 12) and while it is inviting to follow the delimitation in outer continental shelf disputes where the coasts are adjacent, situations with disputing States with opposite coasts may call for deviations (para 13). More importantly, it appears that in Libya/Malta, the ICJ concluded that the reason for which geomorphological characteristics were immaterial in the delimitation of areas where the distance between the coast is less than 400 M, is due to the fact that there is no “reason why a factor which has no part to play in the establishment of title should be taken into account as a relevant circumstance for the purposes of delimitation” (para 40). A fortiori, such characteristics may arguendo be given a role in disputes where the ´establishment of title` relies on geomorphology and geology. The applicant in the NICOL cases may under this assumption be seen to have made a strong and valid argument, notwithstanding courts and tribunals rulings suggesting the contrary (para 526). However, to accept the proposition of the applicant in the NICOL cases, would ignore the fact that the above finding of the ICJ in Libya/Malta cannot fully be seen to relate to the situation where an overlap arises from an outer continental shelf entitlement of State A that overlaps with the 200 M continental shelf area of State B, where the distance between the coasts is more than 400 M. The overlap would be geometrically variable. State A asserts entitlement to an outer continental shelf that extends into the area landward of the 200 M distance line of State B, while State B refrains from making an outer continental shelf claim as it relies only on the 200 M distance entitlement. The putative overlap of entitlements would, as was the case in NICOL II, be located wholly landward the 200 M distance line of State B, while the median line, constructed on the basis of relevant basepoints, would be located beyond the area with the putative overlapping entitlements. The operative paragraph in Libya/Malta is instructive for clarifying whether such an overlap is permissible under international law.

A Redundant Exercise? 

In the dissenting opinion of Judge Charlesworth in NICOL II, the view was put forward that the preservation of the 200 M zone to the relevant State party to a delimitation dispute “may constitute a relevant circumstance warranting the adjustment of the provisional equidistance line at the 200-nautical-mile” (para 33). Yet, the provisional equidistance line, constructed on the basis of geometry from relevant basepoints of the mainland coasts of Colombia and Nicaragua was not even located in the area of putative overlaps of entitlement. Therefore, it is difficult to see how, and for which purpose, any such provisional equidistance line should be ´adjusted [..] at the 200 [M] line`. Further, this opinion of the learned Judge would also appear to ignore the rule recalled in the Black Sea case that “the task of delimitation consists in resolving the overlapping claims by drawing a line of separation of the maritime areas concerned” (para 77). To attribute the 200 M area to the relevant State under the second-stage of the delimitation methodology, under the guise of a relevant circumstance, would pay lip service to the understanding that the object of a court or tribunal seized in a delimitation dispute “is to define the boundary line between the areas under the maritime jurisdiction of two States” in which the “the sharing-out of the area is therefore the consequence of the delimitation” (para 64). Further, in the decision on merits in NICOL, in 2012, the ICJ observed that delimitation “consists in resolving the overlapping claims by drawing a line of separation between the maritime areas” (para 141) [emphasis added]. The formula suggested by Judge Charlesworth would not, to rely on the expression in Black Sea, be ´drawing a line of separation` as Colombia did not put forward a claim to the area beyond its 200 M distance line. Consequently, there would be no delimitation under that hypothesis.

The operative paragraph in Libya/Malta is key for addressing the question whether it would be ´legally possible` for an outer continental shelf entitlement to extend into the 200 M zone of the neighboring State with an opposite coast. Explaining its reasons for dismissing the relevance of geomorphology, the ICJ concluded that for “the area of continental shelf to be found to appertain to either Party not extending more than 200 miles from the coast of the Party concerned, no criterion for delimitation of shelf areas can be derived from the principle of natural prolongation in the physical sense” (para 79.A.2) [emphasis added]. The ICJ relies on the conjunction ´either`. Accordingly, under this understanding it is not allowed to attribute any role to natural prolongation in a delimitation in so far concerns areas within the 200 M distance line of either of the disputing States. Accordingly, it is difficult to accept the proposition that outer continental shelf entitlements may extend into the 200 M zone of a neighboring State with an opposite coast. This arises as it is uncontested that the delimitation in such a dispute could not be effectuated without attributing ´natural prolongation in the physical sense` (para 79.A.2) a role in the delimitation. This leads to the assertion that the operative paragraph in Libya/Malta supports the conclusion as such, without being obliged to seek the determination of a customary rule of international law, that under general international law an outer continental shelf entitlement cannot extend into the 200 M zone of a neighboring State with an opposite coast. This understanding is supported in the relevant excerpt from the above-mentioned operative paragraph in Libya/Malta. In fact, this ruling in Libya/Malta, which regrettably appears given little attention in the NICOL cases is not only tantamount to, but actually does imply, that it is not legally possible for State A to make a claim based on natural prolongation within the area landward the 200 M distance line of State B. In the words of the ICJ in Tunisia/Libya, the “need for delimitation of areas of continental shelf between the Parties can only arise within the submarine region in which claims by them to the exercise of sovereign rights are legally possible according to international law” (para 34). 

Equity

In this regard it is also of interest to recall that the reason for which the exploitability criterion was included in the Geneva Convention on the Continental Shelf was, to quote H. Lauterpacht in a paper published in the British Yearbook on International Law in 1950, due to the proposition that it would be “unjust to countries having no continental shelf” only to rely on the 200 metres depth criterion. To the same extent as was the case with the exploitability criterion, the distance-based criterion in Article 76(1) has a similar equitable function, i.e. to ensure that a minimum area of continental shelf is attributed to States notwithstanding the physical characteristics of the seabed. In this regard, Judge Aréchaga observed in his separate opinion in Tunisia/Libya that with UNCLOS, the exploitability criterion in the Geneva Convention “has now been replaced by a criterion stated in terms of distance, which has the same objective. It is safe to assert that today the distance test of 200 M has abrogated the exploitability test” (para 52). On this very notion, Judge Oda also noted in his dissenting opinion in Libya/Malta that the 200 M distanced-based entitlement emerged during the Third Conference as “a minimum expanse of the reserved sea-bed areas even beyond their geologically limited continental shelf” (para 52). Finally, Judge Jiménez de Aréchaga observed also in his separate opinion in Tunisia/Libya, upon ascertaining that the distance criterion in Article 76(1) had replaced the exploitability criterion, that “it would be unthinkable that a State would try to exploit the submarine areas off the coasts of another State at less than 200 [M] from the shore” (para 53). Yet, this unthinkable scenario would, in an analogical fashion, occur in the event the ICJ were to accept the proposition that a delimitation may arise where an overlap occurs between two States with opposite coasts that are more than 400 M from each other and where only one of the two States asserts outer continental shelf entitlement. The ICJ disallowed this possibility already in 1985 by concluding in the operative paragraph that no criterion based on natural prolongation can be taken into account in the delimitation of continental shelf areas of ´either` of the States parties to a delimitation dispute.

The practice of States having transmitted proposed outer limits of the continental shelf to the CLCS demonstrates at least that it appears unreasonable or unnatural to claim outer continental shelf entitlements within 200 M zones of third States. In the words of the former President of the ICJ, R. Jennings, “the function of equity is precisely to qualify rules of law when their application in particular circumstances would produce ´extraordinary, unnatural or unreasonable` results” (Robert Y. Jennings, “The Principles Governing Marine Boundaries”, K. Hailbronner et a. (eds.), Festschrift für Karl Doehring, p. 399). Further, as observed by the ICJ in Tunisia/Libya, the “legal concept of equity is a general principle directly applicable as law” (para 71) in the international legal order. Accordingly, applying equity in international law is not ex aequo et bono, which requires the consent of both Parties for a court or tribunal to judge accordingly. On that note, it is difficult to disagree with the interpretation, ascertained by Judge Aréchaga and Judge Oda that the distance constraint in Article 76(1) has a similar function as the 200 metres depth criterion in Article 1 of the Geneva Convention, i.e. establishing a de minimis area, whose very conception would be rendered nugatory were outer continental shelf entitlements to encroach such areas.

Grey Areas

There are a number of disputes between States with adjacent coasts in which an equidistance line is shifted during the first or second stage of the delimitation methodology, which consequently results in a so-called grey area, ie. an area within which State A has only Exclusive Economic Zone (EEZ) jurisdiction while the seabed underneath the EEZ is the continental shelf of State B, but beyond the 200 M distance line from its baselines. This situation arose e.g. in the Bay of Bengal, the Bay of Bengal Maritime Arbitration and also in the Somalia v. Kenya.

The proposition could be put forward that the acceptance of grey areas implies necessarily that international law does allow outer continental shelf entitlements to extend within 200 M entitlement zones of neighboring States. Following the reasoning of Judge Charlesworth, to the extent the approach of the ICJ in NICOL II would have been followed in Somalia v. Kenya and also by the International Tribunal for the Law of the Sea (ITLOS) and the arbitral tribunal, respectively, in the two Bay of Bengal maritime delimitation disputes, the submissions of Bangladesh and Kenya, in so far that these resulted in grey areas should have been “declared inadmissible” at the outset (para 21). Further, according to Judge Tomka, the acceptance of grey areas implies necessarily as a “matter of legal principle, a State’s entitlement to a continental shelf beyond 200 nautical miles may extend within 200 nautical miles from the baselines of another State” (para 47). The author to this blog is of the view that the above reservations to the majority decision have some merit if one is to rely on the rationale that appears in the majority decision in NICOL II. However, it is important to note that where the coasts are adjacent, the creation of grey areas did not result as a consequence of attributing ´natural prolongation in the physical sense` (para 79.A.2) any role in the adjustment of the provisional equidistance line. Such adjustments were made because of reasons that relate to the coastal configurations. Accordingly, the point of fact that grey areas have arisen in delimitation disputes between States with adjacent coasts is not dispositive for allowing outer continental shelf entitlements to overlap areas landward the 200 M distance line of a neighboring State with an opposite coast. Quite the contrary. Such areas result from seeking equitable results that are based on objective and equitable criteria, consistent with the firm case law of courts and tribunals ever since the Libya/Malta decision.  

Concluding Observations

Notwithstanding whether there is support for the suggested interpretation presented in this post, one is tempted to ask whether there was, in any event, a need to wait 11 years, after the NICOL ruling on the merits in 2012 to render the judgment in July 2023 in NICOl II. As recognized by the ICJ in Tunisia/Libya, the “need for delimitation of areas of continental shelf between the Parties can only arise within the submarine region in which claims by them to the exercise of sovereign rights are legally possible according to international law” (para 34). Accordingly, the question arises why after having concluded in 2012 in NICOL that “Nicaragua has not established” (para 129) that its claimed entitlement extended into the 200 M distance zone of Colombia, the ICJ observed that it “need not address any other arguments developed by the Parties, including the argument as to whether a delimitation of overlapping entitlements which involves an extended continental shelf of one party can affect a 200-nautical-mile entitlement to the [CS] of another party” (para 130). However, it should be noted that upon the reading of the judgment on merits in NICOL, only 61 submissions had been transmitted to the CLCS, whereas the number was 93 upon the reading of the judgment in July 2023 in NICOL II – a relevant fact, which may have resulted in a different outcome, were the ICJ to decide on this question in its judgment on merits in 2012.

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Andrew Serdy says

November 24, 2023

Dear Bjørn
You demonstrate convincingly why there is no incompatibility between the July 2023 judgment and the phenomenon of grey areas in delimitations between adjacent States of the continental shelf beyond 200 miles from the baseline. More generally, though, I worry that, although we are stuck with the Libya v. Malta judgment, it doesn't merit the reverence you and others accord it, not least because it egregiously misunderstands how the structure of UNCLOS Article 76(1) affects the source of a coastal State's entitlement to a continental shelf beyond 200 miles. There was a fine article by Olorundami a few years ago explaining why, even if the Libya v. Malta reasoning were sound, it could only apply where - as in that case - the distance between the opposite coasts is no more than 200 miles (strictly, this should have been 212, but the cogency of the argument is unaffected), not 400 as is commonly assumed. I think you are on the right track with your closing observation, but wonder whether the better comparison is not between the numbers of submissions at the time of the two judgments, but rather between those at the time the cases were brought, 2001 (if I'm not mistaken) and 2013, where the contrast is far more stark.

M Alexianu says

November 27, 2023

Dear Professor Kunoy:

Thank you for this very interesting piece. As the other commentator suggests, I wonder if the Libya/Malta judgment is sufficient to establish a general principle of international law on this point. UNCLOS Article 76(1) does not prioritize either distance or natural prolongation and the Libya/Malta opinion is at best a subsidiary source interpreting this provision (and, as you note, concerned somewhat different circumstances than the ones here). And, since 1985, both the Court (at para. 75 of NICOLII itself) and tribunals have emphasized the concept of a single continental shelf–which seems to undermine the grounds on which the Libya/Malta holding was based.

I suspect these issues might explain why the Court preferred to ground its decision in custom rather than extend the Libya/Malta holding in this context. But in NICOLII, the Court’s methodology appears to go beyond a traditional CIL analysis. In a piece elsewhere (https://www.asil.org/insights/volume/27/issue/9), I’ve suggested that the Court supplemented its inductive analysis of state practice–which, as the dissenting judges noted, is not airtight–with a deductive approach based on the text and logic of the Article 76 regime. This actually parallels the Court’s reasoning in Libya/Malta, where it used the structure of the EEZ and continental shelf regimes to establish the primacy of the distance criterion (paras. 33-34). So, it looks like the Court used a similar methodology to reach a similar result–but this time avoiding the explicit emphasis of distance. (With apologies for linking my own work here, but I wanted to put our pieces in conversation--and welcome your feedback.)

Bjørn Kunoy says

December 1, 2023

Thanks for your valuable comment(s) Andrew.

Re the closing observation to which you allude:

1. It follows jointly from the judgment on merits in 2012 (NICOL) and the judgment on preliminary objections in 2016 (NICOL) that in 2013 by fulfilling the procedural obligation in Art 76(8) the Applicant ´has [..] established that it has a continental margin that extends far enough to overlap with Colombia’s 200-nautical-mile entitlement` (para 129). Due to the fulfilment of the procedural obligation, the third preliminary objection raised by the Respondent in NICOL II was, with the President´s casting vote, determined to be admissible.

2. According to Art 76(3), the ´continental margin` is the submerged prolongation of the land mass of a coastal State.

3. It is by no means easy to accept the proposition that on the one hand it is concluded that the Applicant has established that the submerged prolongation of its land mass ´extends far enough` to overlap with the 200 M zone of the Respondent, and therefore the submission to the ICJ to delimit the alleged overlap is determined to be admissible, albeit on the other hand it follows from the judgment on merits in NICOL II that an outer continental shelf ´may not extend` within the 200 M zone of another State.

One knows about the Baxter Paradox. This must be the NICOL paradox.

Bjørn Kunoy says

December 1, 2023

Thanks Matei for your valuable comments,

Yes, it is well-known that courts and tribunals at different occasions for various reasons identify the existence of CIL by induction or mere assertion. The EJIL paper of professor Talmon is a must read insofar concerns this question. And I believe that the Court´s referral in NICOL II to Gulf of Maine is a testimony of the Courts partial reliance on induction in the identification of the CIL rule in question. Yet, for reasons explained in my post, I believe there was no reason to pursue this undertaking.

I read your ASIL post - very interesting. Thank you for drawing it to my attention.