RecentDevelopmentoftheJurisprudence
Concerning
theDelimitation of the Continental
Shelf beyond 200 Nautical Miles
COLP 46 Istanbul
22 September 2023
Professor Yoshifumi TANAKA
University of Copenhagen27/09/2023

2Introduction► The Delimitation of the Continental Shelf beyond 200 M as a Modern Sphinx:
Three Issues
1. The entitlement to the continental shelf beyond 200 nautical miles (M) that
extends within 200 M from the baselines of another State→ The 2023 Nicaragua v. Colombia case
2. The relationship between the Commission on the Limits of the Continental Shelf(CLCS) and an international court or tribunal→ The 2023 Mauritius/Maldives case
3. The delimitation methodology

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3The Mauritius/Maldives Case
The Standard of Significant Uncertainty►The Bangladesh/Myanmar case
‘Notwithstanding the overlapping areas indicated in the submissions of
the Parties to the Commission, the Tribunal would have been hesitant toproceed with the delimitation of the area beyond 200 nm had it
concluded that there was significant uncertainty as to the existence of acontinental margin in the area in question’ (ITLOS Reports 2012, 115, para. 443).
►The Mauritius/Maldives case
‘The Special Chamber will apply the standard of significant uncertainty

in the present case’ (para. 433).

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4The Mauritius/Maldives Case
The Standard of Significant Uncertainty► Two Reasons
1. To minimize the risk of conf licts between the views of the CLCS and ITLOS‘It notes that this standard serves to minimize the risk that the CLCS mightlater take a different position regarding entitlements in its
recommendations from that taken by a court or tribunal in a judgment’(para. 433).

2. The safeguard of the Area‘[I]n maritime delimitation cases, international courts and tribunals refrainfrom delimiting areas where the rights of other coastal States may beaffected. Application of the standard of significant uncertainty affords
similar protection to the interests of the international community in theArea and the common heritage principle’ (para. 453).

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The Mauritius/Maldives Case
The Standard of Significant Uncertainty►The Scope of the Application of the Standard of Significant Uncertainty•The Bangladesh/Myanmar judgment: The standard of significant uncertainty
would not be applied to the circumstances where, like the Bay of Bengal, there is‘uncontested scientific evidence’.
• The standard of significant uncertainty may come into play in the situation
where scientific evidence regarding entitlements to a continental shelf beyond
200 M is contested by one of the disputing parties and/or scientific evidence isdebatable or absent.

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The Mauritius/Maldives Case
The Standard of Significant Uncertainty►The Effect of the Agreement between the Parties• The 2021 Somalia v. Kenya case‘[I]n their submissions to the Commission both Somalia and Kenya claim on
the basis of scientific evidence a continental shelf beyond 200 nautical miles,
and that their claims overlap’ (ICJ Reports 2021, para. 194).
‘[N]either Party questions the existence of the other Party’s entitlement to acontinental shelf beyond 200 nautical miles or the extent of that claim’(Ibid).
→The ICJ decided that it would proceed the delimitation of the continental
shelf beyond 200 M.

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7The Mauritius/Maldives Case
The Standard of Significant Uncertainty►The Effect of the Agreement between the Parties: Critiques• Judge Donoghue’s view‘[T]he Court has scant evidence regarding the existence, shape, extent and continuity of any
outer continental shelf that might appertain to the Parties.’ (Separate Opinion of President
Donoghue, ICJ Reports 2021, 286-287, para. 4).

• Judge Robinson’s view‘[N]owhere in the Judgment is there any analysis of that content to show that the Court issatisfied that the necessary geological and geomorphological criteria have been met for theexistence of a continental shelf beyond 200 nautical miles’ (Individual Opinion, Partly
Concurring and Partly Dissenting, of Judge Robinson, ICJ Reports 2021, 329, para. 14).
→Possibility of the application of the standard of significant uncertainty (?)

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8The Mauritius/Maldives Case
The Standard of Significant Uncertainty► The Criterion for the Standard of Significant Uncertainty• ITLOS Special Chamber’s view
‘Given the significant uncertainty, the Special Chamber is not in a position
to determine the entitlement of Mauritius to the continental shelf beyond
200 nm in the Northern Chagos Archipelago Region’ (para. 450).
‘[I]n the circumstances of this case, it would not be appropriate to arrange
for such an [expert] opinion’ (para. 454).
• Judge Hider’s view
‘In my view, an expert opinion would have served to strengthen thescientific and technical basis for the Special Chamber’s conclusions withrespect to the second and third routes advanced by Mauritius…’ (Declarationof Judge Heider, para. 30)

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9The Nicaragua v. Colombia Case
Assessment of Customary International Law► The ICJ’s questions in its Order of 4 October 2022
(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 ofits territorial sea is measured extend within 200 nautical miles from thebaselines of another State?
(2) What are the criteria under customary international law for the determinationof the limit of the continental shelf beyond 200 nautical miles from thebaselines from which the breadth of the territorial sea is measured and, in thisregard, do paragraphs 2 to 6 of Article 76 of the United Nations Convention
on the Law of the Sea ref lect customary international law?

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10The Nicaragua v. Colombia Case
Assessment of Customary International Law► Assessment of General State Practice• Colombia: Some 55 submissions could have extended within the 200-nauticalmile zones of other States, but 51 of those 55 submissions stopped at the 200nautical-mile entitlements of neighbouring States when they could have gone
further on technical grounds.
• The ICJ: ‘Taken as a whole, the practice of States may be considered sufficiently
widespread and uniform for the purpose of the identification of customaryinternational law’ (ICJ Reports 2023 (not yet reported), para. 77).
• Critique by Judge Tomka: ‘[T]he Judgment does not acknowledge, much lessanalyse, the existence of contrary State practice whereby States have claimed acontinental shelf entitlement that extends within 200 nautical miles from thebaselines of another State’ (Dissenting Opinion of Judge Tomka, para. 42).

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The Nicaragua v. Colombia Case
Assessment of Customary International Law► Assessment of General State Practice• Judge Tomka‘[S]ome inconsistencies and contradictions are not necessarily fatal to afinding of “a general practice”’ (Dissenting Opinion of Judge Tomka, para.
42).

• Judges Robinson‘There is therefore practice that can be considered sufficiently widespreadand uniform’ (Dissenting Opinion of Judge Robinson, para. 13).
• Judge Charlesworth‘This practice appears to be a general one’ (Dissenting Opinion of JudgeCharlesworth, para. 26).

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The Nicaragua v. Colombia Case
Assessment of Customary International Law► Assessment of Opinio Juris• ICJ’s view
‘The Court considers that the practice of States before the CLCS isindicative of opinio juris, … In addition, given its extent over a long periodof time, this State practice may be seen as an expression of opinio juris,which is a constitutive element of customary international law’ (ICJ Reports
2023 (not yet reported), para. 77).

‘[U]nder customary international law, a State’s entitlement to a continental
shelf beyond 200 nautical miles from the baselines from which the breadthof its territorial sea is measured may not extend within 200 nautical miles
from the baselines of another State’ (Ibid., para. 79).

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The Nicaragua v. Colombia Case
Assessment of Customary International Law► Critiques• Judge Tomka‘Today’s Judgment does not acknowledge the existence of clear expressionsof opinio juris to the effect that a State’s entitlement to a continental shelfbeyond 200 nautical miles may extend within 200 nautical miles from thebaselines of another State’ (Dissenting Opinion of Judge Tomka, para. 59).
• Judge Xue‘There is no evidence shown in the Judgment that those States parties, whenrestricting their claim in the submissions, believed that such restraint wasrequired by a legal obligation or guided by law’ (Separate Opinion of Judge Xue, para. 47).

• Judge Robinson‘[T]here is no basis for deriving opinio juris from State practice relied upon’(Dissenting Opinion of Judge Robinson, para. 19).

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The Nicaragua v. Colombia Case
Assessment of Customary International Law► Flexible Assessment of Opinio Juris by the ICJ• The North Sea Continental Shelf cases

The customary law character of the equidistance method: application of arigid approach to the assessment of opinio juris
The equitable principles: No application of the rigid test of the two elements→ An opinio juris as a f lexible tool to either confirm or deny a rule ofcustomary international law• The Nicaragua case (Merits)‘This opinio juris may,… be deduced from, inter alia, the attitude of the Parties
and the attitude of States towards certain General Assembly resolutions,…’ (ICJReports 1986, 99-100, para. 188)

→ An opinio juris as a tool to safeguard a rule of customary international law
ref lecting community interests27/09/2023

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The Nicaragua v. Colombia Case
Assessment of Customary International Law► Two Approaches to the Assessment of Opinio Juris• The rigid (or positivist) approach: Judges Tomka, Robinson, and Xue• The f lexible (or teleological) approach: The majority opinion
Judge Iwasawa’s view:‘States usually do not curtail themselves when they believe that they have aright. If an issue is regulated by international law and States abstain fromcertain conduct in a way that is inconsistent with their own interests, it may bepresumed that their abstention is motivated by a sense of legal obligation’( Separate Opinion of Judge Iwasawa, para. 12).

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The Nicaragua v. Colombia Case
The Inter-relationship between the EEZ and the Continental Shelf► The ICJ’s view in the Libya/Malta case
‘Although the institutions of the continental shelf and the exclusive
economic zone are different and distinct, the rights which the exclusive
economic zone entails over the sea-bed of the zone are defined by reference
to the régime laid down for the continental shelf. Although there can be acontinental shelf where there is no exclusive economic zone, there cannot
be an exclusive economic zone without a corresponding continental shelf ’(ICJ Reports 1985, 33, para. 34).

•The continental shelf as part of the EEZ: to separate the continental shelffrom the superjacent waters within 200 M is inconsistent to the concept ofthe EEZ itself

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The Nicaragua v. Colombia Case
The Inter-relationship between the EEZ and the Continental Shelf► The exclusive nature of Sovereign Rights over the EEZ• The ITLOS Special Chamber’s view in the Mauritius/Maldives case‘[N]either Party may claim or exercise sovereign rights or jurisdiction withrespect to the exclusive economic zone or the continental shelf within the200 nm limit of the other Party on the latter’s side of the boundary’ (para.
274).

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The Nicaragua v. Colombia Case
The Inter-relationship between the EEZ and the Continental Shelf► The distance criterion as the only legal title to the continental shelf within 200 M• The ICJ’s view in the Libya/Malta case‘[W]here verification of the validity of title is concerned, since, at least in so
far as those areas are situated at a distance of under 200 miles from the coasts
in question, title depends solely on the distance from the coasts of theclaimant States of any areas of sea-bed claimed by way of continental shelf,
and the geological or geomorphological characteristics of those areas arecompletely immaterial’ (ICJ Reports 1985, 35, para. 39).

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19The Nicaragua v. Colombia Case
The Inter-relationship between the EEZ and the Continental Shelf► The Integrity between the EEZ and the Continental Shelf• The ICJ’s view in the 1985 Libya/Malta case‘[T]he two institutions—continental shelf and exclusive economic zone—are linked

together in modern law’ (ICJ Reports 1985, 33, para. 33).
• Judge Oda’s view in the Tunisia/Libya case

‘Article 56, paragraph 3, should be interpreted to mean that the régime of theexclusive economic zone will incorporate, in principle, the whole regime of thecontinental shelf ’ (Dissenting Opinion of Judge Oda, ICJ Reports 1982, 234-235, para. 130).

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The Nicaragua v. Colombia Case
The Inter-relationship between the EEZ and the Continental Shelf► The Integrity between the EEZ and the Continental Shelf• Judge Iwasawa’s view in the 2023 Nicaragua v. Colombia case‘[T]the régime of the exclusive economic zone affords a strong basis for theconclusion that the outer continental shelf of a State may not extend within 200
nautical miles of another State’ (Separate Opinion of Judge Iwasawa, para. 7).

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The Nicaragua v. Colombia Case
The Grey Area

► The Grey Area: the marine spacebeyond the 200 M limit of one Statebut within that of the other State yeton the side of the former State of themaritime boundary

Source: The Bangladesh v. India case, Award of 7
July 2014, p. 159.
https://pcacases.com/web/sendAttach/383

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The Nicaragua v. Colombia Case
The Grey Area
► The ICJ’s view
‘In the two Bay of Bengal cases, the use of an adjusted equidistance line in adelimitation between adjacent States gave rise to a “grey area” as anincidental result of that adjustment. … The Court considers that theaforementioned decisions are of no assistance in answering the firstquestion posed in the present case’ (para. 72).
► Judge Xue’s view‘[T]he “grey area”, albeit incidental in nature and small in size, is in itself apiece of hard evidence that disproves at least the inseparability of the twozones in the maritime delimitation’ (Separate Opinion of Judge Xue, para. 27).

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The Nicaragua v. Colombia Case
The Grey Area
► The ITLOS Special Chamber’s view in the Mauritius/Maldives case‘[N]either Party may claim or exercise sovereign rights or jurisdiction withrespect to the exclusive economic zone or the continental shelf within the200 nm limit of the other Party on the latter’s side of the boundary.
Therefore, the boundary has the effect of rendering moot the question ofdelimitation of the area of overlap between the claim of the Maldives to acontinental shelf beyond 200 nm and the claim of Mauritius to a 200 nmzone’ (para. 274).
► Judge Charlesworth’s view in the Nicaragua v. Colombia case‘[U]nder the applicable rules on maritime delimitation, an entitlement to an
extended continental shelf in principle shall be given no effect in so far as it
overlaps with another State’s entitlement to a 200-nautical-mile zone’(Dissenting Opinion of Judge Charlesworth, para. 31).

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The Nicaragua v. Colombia Case
The Grey Area
► Dr. Rao’s view in the Bangladesh v. India case
‘The creation of a grey area is entirely contrary to law and the policies
underlying the decision taken in UNCLOS to create the EEZ as one single,
common maritime zone within 200 nm which effectively incorporates theregime of the continental shelf within it’ (Concurring and Dissenting Opinion of
Dr. P.S. Rao para. 24).

► Judge Lucky’s view in the Bangladesh/Myanmar case‘[T]he result of a strict interpretation of the law set out in Parts V and VI ofthe Convention prohibits any allocation of one area to the other’ (Dissenting
Opinion of Judge Lucky, ITLOS Reports 2012, 285).

Conclusion
1. The ICJ’s approach in the Nicaragua v. Colombia case
Under customary international law, a State’s entitlement to a continental
shelf beyond 200 M may not extend within 200 M from the baselines ofanother State.
2. The ITLOS Special Chamber’s approach in the Mauritius/Maldives caseNo legal effect shall be given to the entitlement to the continental shelfbeyond 200 M when it extends within 200 M from the baselines of anotherState.
→Prevention of complex issues arising from the separation of legal regimes
governing the seabed/subsoil and its superjacent waters
Yoshifumi Tanaka ©2023