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  • JTMS Intern Vasiliki Lampiri

Could Maritime Delimitation Agreements be Terminated in the Face of Sea-Level Rise?

Updated: Aug 29, 2023

Homes pack an atoll in the Marshall Islands. Photo from the LA Times, Carolyn Cole


The last three decades the international community has been extremely concerned about the effects of climate change and the rising seas. Sea-Level Rise will physically affect the environment, leading to coastline erosion, flooding of wetlands, inundation of deltas and will bring habitats and local communities into danger. Undoubtedly, sea-Level Rise’s effects challenge several branches of international law, including among others human rights law, the law of statehood, and most importantly the law of the sea. Much ink has been spilled on whether and how sea-level rise will affect maritime limits and boundaries. To this end, this blog post focuses specifically on whether boundaries established by bilateral maritime delimitation agreements can be terminated owing to coastal change.


International legal bodies, such as the International Law Commission (ILC) and the International Law Association (ILA), but also prominent legal scholars have already concluded that the baselines from which the maritime zones are measured are ambulatory[i], that is, they shift to reflect the changes occurring to the coastline. As a result, unilateral maritime limits either move landward due to sea-level rise, or seaward due to land rise and accretion. The question however that arises is whether the boundaries established by agreements follow the same logic, that is, whether theses boundaries have to change due to sea-level rise.


Generally, treaties and judicial decisions are binding upon parties and enjoy permanence due to the principles pacta sunt servanda and res judicata respectively[ii]. Yet, the Vienna Convention on the Law of the Treaties (VCLT) recognizes that a material breach of the treaty, impossibility of performance, a fundamental change of circumstances, or the emergence of a jus cogens rule which is in conflict with the terms of the treaty, are considered solid grounds that may lead to the termination of a treaty[iii].


Given the pivotal role of coastal geography on maritime delimitation, the most likely grounds for the termination of a treaty in the case of sea-level rise is the invocation of a fundamental change of circumstances under Article 62 of the VCLT[iv]. However, Article 62(2)(a) precludes the invocation of the principle “if the treaty establishes a boundary”. Indeed, jurisprudence has confirmed that “the continued existence of a boundary is not dependent upon the continuing life of the treaty” that established it, while stability and finality -primary objectives of a frontier- cannot be fulfilled if the boundary line can at any time be challenged[v]. Therefore, the boundary remains in place even if the treaty is terminated.


Article 62(2)(a) does not clarify whether the term boundary covers ‘maritime boundaries’ as well. Some scholars answer this in the negative because the ILC drafts in 1966 did not refer to maritime agreements, while only few such agreements had been concluded back then[vi]. I firmly believe that this view is incorrect. Although customarily the word boundary refers to the limit of the land territory, the ILC has accepted that it could be taken more broadly[vii]. Going one step further, the United Nations Handbook on Maritime Delimitation, without making any distinction on the various maritime zones, maintains that maritime delimitation agreements -like any other boundary treaty- “have a vocation of permanence and stability[viii]”. Therefore, it accepts the permanency for all zones.


The ILC had recognised that the territorial sea limit is a “true limit” but left unclear whether Article 62(2)(a) applies to it[ix]. However, given that state sovereignty extends from the land to the territorial sea and archipelagic waters under Article 2(1) of UNCLOS, I believe that any discussion that excludes territorial sea and archipelagic boundaries from the application of Article 62(2)(a) has no legal basis. Moreover, the Aegean Sea case clearly stated that both land frontiers and continental shelf boundaries enjoy permanency and stability and fall under the exception of the rebus sic stantibus clause[x]. After all, the continental shelf relates to the territorial status[xi] because it is the natural prolongation of the land territory, that is, the land territory beneath water. Even the unilateral continental shelf limits are permanent through Articles 76(8)-(9) of UNCLOS. Consequently, any discussion that outlaws the application of Article 62(2)(a) for territorial sea or continental shelf boundary agreements is pointless.


Furthermore, the Bangladesh/India case affirmed that the effects of climate change cannot jeopardize the settled maritime boundaries established by agreement or adjudication[xii]. The timing of this judicial decision is quite interesting. Contrary to the Aegean Sea ruling, the Bangladesh/India case came out in a period that the international community had already engaged in the discussion regarding the impacts of sea-level rise on oceanic boundaries. The general wording used by the Tribunal and the fact that it decided the course of all zones (including the EEZ) allows us to extrapolate that all zones without any distinction are not affected by sea-level rise and fall under Article 62(2)(a). Rejecting the application of the ‘boundary exception’ for zones beyond the TS -as Arnadottir appears to suggest[xiii]- “builds upon a formalistic distinction between boundaries in different maritime zones”[xiv]. But nowadays States tend to draw a single maritime boundary for all zones, which makes it more difficult to separate the regime of the continental shelf from that of the EEZ. All the more, once proclaimed, the EEZ incorporates the continental shelf regime, and thus Arnadottir’s approach complicates States’ exercise of rights in these zones[xv]. To date there are only three occasions where the continental shelf and EEZ boundaries do not coincide[xvi]. Despite the disparity between the extent of the rights enjoyed in the continental shelf compared to the EEZ, Article 83 for the continental shelf delimitation repeats verbatim Article 74 for EEZ delimitation. There is no indication that States sought to privilege the continental shelf boundary line over the EEZ one. Moreover, Arnadottir’s argument that maritime boundary treaties should not equate to treaties establishing land boundaries because the latter’s objective is stability while the former’s is the equitable solution[xvii] is a fallacy. An equitable solution does not preclude a stable solution. Hence, at least as regards the delimitation agreements, States adhere not to differentiate the two zones.


Environmental changes, such as the drying up of a river have been referred to as examples that could justify the invocation of a fundamental change of circumstances, if the other conditions are met[xviii]. However, even without the ‘boundary exclusion’ in Article 62(2)(a), it would be extremely difficult for States to terminate a maritime boundary treaty due to sea-level rise on the basis of Article 62(1)[xix]. For a fundamental change of circumstances to be invoked successfully, the conditions embodied in Article 62(1) must be fulfilled cumulatively, rendering the burden exceptionally high for a State to meet. Specifically, this change of circumstances must be fundamental, unforeseen by the Parties at the time the treaty was concluded and simultaneously the circumstances that changed must constitute an essential basis of the consent of the parties and radically transform the extent of their obligations[xx].


Sea-level rise is widely known since the 1980s and thus at least for the treaties that were concluded thereafter it cannot qualify as an unforeseen situation. Even the doubts on whether the EEZ agreements enjoy permanency should be rejected as the EEZ was an innovation of UNCLOS and most agreements were signed during the last forty years. Second, it is unchallenged that sea-level rise brings geographical changes. Yet, this is not crucial. What matters is whether the initial geographical circumstances were the basis of Parties’ consent. Although it cannot be denied that coastal geography is central in delimitation, it is doubtful -contrary to what Arnadottir argues[xxi]- whether it forms the essential basis of the consent to be bound. Most agreements specify the boundary’s geographic coordinates but lack references to the motivation or methodology used to reach that agreement, making it impossible for States to convince that that precise coastline configuration was the basis of their consent[xxii]. Agreements without coordinates, which specify only the method of delimitation (e.g., equidistance) could theoretically be vulnerable owing to sea-level rise due to the ‘ambulation’ of baseline. Yet, to date there is only one such agreement, namely, the 1980 France-Tonga EEZ Agreement, since the 1985 France-Tuvalu agreement has already been replaced[xxiii]. It can also be argued that geographical change is inherent to maritime delimitation agreements, and thus geographic stability is not itself the grounds for the consent of the Parties[xxiv]. Interestingly case-law deems future coastline instability irrelevant to the delimitation process[xxv]. Lastly, Parties would unlikely convince that the change radically transformed their obligations, or that it substantially hindered the realisation of the object and purpose of the treaty, on which, after all, the consent to be bound was based. The disappearance of some basepoints would probably not have significant effect on Parties’ obligations under the treaty because their obligation is primarily the observance of the boundary.[xxvi] Undoubtedly, charts could still assist in locating the boundary line. sea-level rise would not have any effect on maritime delimitation agreements, unless a major island disappears completely beneath water, making it impossible for States to locate the boundary. On that case, however, States could resort to VCLT’s Article 61(1) and invoke impossibility of performance.


Undoubtedly, States are free to revise a maritime boundary treaty. Article 2(5) of the Micronesia-Marshall Islands treaty, for example, provides that States can agree to revise the boundary’s coordinates if significant shifts in the location of islands used as basepoints occur[xxvii]. However, to date, this seems to be the exception, rather than the rule. Out of 250 maritime delimitation treaties, the vast majority of them do not include amendment provisions and certainly none provides for the explicit adjustment due to sea-level rise[xxviii]. Moreover, some agreements expressly include provisions on the permanent character of the delimitation[xxix]. Based on that, both the ILA and the ILC concluded that neither can sea-level rise constitute a fundamental change of circumstances, nor endanger the validity of maritime boundary treaties[xxx]. The fact that to date no State has requested the termination of such a treaty due to sea-level rise confirms that States have favoured stability, certainty, security, and predictability in maritime boundaries. Most scholarship supports the above conclusion[xxxi]. This stability led some scholars to recommend the conclusion of maritime agreements as a viable solution against sea-level rise. However, this option is of no great avail for Small Island Development States (SIDS) that are geographically secluded. Out of 427 potential maritime boundaries, only 168 have already been delimited, from which only 45 are in the Pacific[xxxii]. Nauru, for example, borders the High Seas in the west, and thus negotiating a boundary treaty is not possible.


In any case, International Court and Tribunals (ICTs) are particularly reluctant to accept unilateral termination based on a fundamental change of circumstances, while this has never been successfully invoked before the International Court of Justice (ICJ)[xxxiii]. The negative and conditional wording of Article 62 clearly indicates that the plea of should be applied only in exceptional cases[xxxiv]. Therefore, accepting it as a general rule for all maritime delimitation agreements in the face of sea-level rise goes against both the real purpose of VCLT’s Article 62, but also against the objective that lies behind UNCLOS as a whole, that is, the “strengthening of peace, security, cooperation and friendly relations”[xxxv]. The latter may be at stake because the potential termination of all these boundary treaties will create a fertile ground for international conflicts. Negotiating a maritime boundary is a complex, time-consuming and rarely an easy process. As a corollary, instead of challenging the initial boundary (and generally the law of the sea framework), I would recommend states, which are unsatisfied with the effects of sea-level rise on their coasts, to resort to the conclusion of Joint Development Agreements (JDAs) around the boundary line. This would be in line with the principle of good faith and will deprive states of potential conflict.


In conclusion, irrespective of whether the ambulatory theory is accepted or not for the unilateral limits, the boundaries established by agreements are protected in the face of Sea-Level Rise. Article 62(2)(a) excludes the termination of maritime boundary agreements. Yet, even without this article, the general rule of article 62 regarding the fundamental change of circumstances and the need to fulfill all conditions embodied therein cannot be reached.


By JTMS Intern Vasiliki Lampiri


*** The views expressed herein belong solely to the author and do not necessarily represent the opinions of JTMS or Yonsei Institute for North Korean Studies. ***

[i] International Law Commission ‘Sea-Level Rise in relation to International Law: First Issues Paper by Bodgan Aurescu and Nilufer Oral’, A/CN.4/740, 2020, p.28, para.78; International Law Association, ‘Baselines under the International Law of the Sea’, Sofia Conference, 2012, p.31. [ii] VCLT (1969) Art.26. [iii] VCLT, (1969) Articles 60, 61, 62, 64 respectively. [iv] The article reflects custom. See Fisheries Jurisdiction Case (United Kingdom v. Iceland), Judgment of 2 February 1973, ICJ Reports, p.19, para.36. [v] Case Concerning the Territorial Dispute Libyan Arab Jamahiriya v. Chad (1994), Judgment of 3 February 1994, ICJ Reports, p. 35, paras.72-73; Case Concerning the Temple of Preah Vihear (Cambodia v. Thailand), Merits, Judgment of 15 June 1962, p.34. [vi] Stuart Kaye, ‘The LOS Convention and Sea-Level Rise after the South China Sea Arbitration’, 93 International Law Studies 423 (2017), pp. 438-439. [vii] Yearbook International Law Commission 1982, Volume II, Part II, available at https://legal.un.org/ilc/publications/yearbooks/english/ilc_1982_v2_p2.pdf , last accessed October 28, 2022, p.60 [viii] UNDOALOS, ‘Handbook on the Delimitation of Maritime Boundaries’ (2000), Division for Ocean Affairs and the Law of the Sea-Office of Legal Affairs, p.82, para.322. [ix] Yearbook International Law Commission 1982, Volume II, Part II, available at https://legal.un.org/ilc/publications/yearbooks/english/ilc_1982_v2_p2.pdf , last accessed October 28, 2022, p. 61. [x] Aegean Sea Continental Shelf Case (Greece v. Turkey), Judgment, ICJ Reports 1978, pp.36-37, para.85. [xi] Ibid, p.36, para.83. [xii] In the Matter of the Bay of Bengal Maritime Boundary Arbitration between the People’s Republic of Bangladesh and the Republic of India (Bangladesh v. India), Permanent Court of Arbitration, Award, 7 July 2014, p.63. para.217. [xiii] Snjolaug Arnadottir, ‘Effects of Sea-Level Rise on Agreements and Judgments Delimiting Maritime Boundaries’ in Heidar (ed), New Knowledge and Changing Circumstances in the Law of the Sea BRILL-Nijhoff, 2020, p.404 [xiv] Massimo Lando, Stability of maritime boundaries and the challenge of geographical change: a reply to Snjolaug Arnadottir, Leidan Journal of International Law, Vol 35, Issue 2, 2022, p.13. [xv] Ibid. [xvi] Ibid. [xvii] Snjolaug Arnadottir ‘Termination of Maritime Boundaries due to a Fundamental Change of Circumstances’, Utrecht Journal of International and European Law 32(83), 2016, p.106. [xviii] Snjolaug Arnadottir, Climate Change and Maritime Boundaries: Legal Consequences of Sea-Level Rise, Cambridge University Press, 2021, p. 212. [xix] Kate Purcell, Maritime Jourisdiction in a changing Climate, in Michael Gerrard and Katrina Fisher Kuh The Law of Adaptation to Climate Change: US and international aspects, American Bar Association, 2012 p.758; Julia Lisztwan, Stability of Maritime Boundary Agreements, 37 Yale Journal of International Law, 2012, p.184; Robin Churchill, Vaughan Lowe, Amy Sander, The Law of the Sea (4th edition), Manchester University Press, 2022, p. 368. [xx] VCLT, Article 62(1). [xxi] Snjolaug Arnadottir, ‘Effects of Sea-Level Rise on Agreements and Judgments Delimiting Maritime Boundaries’ in Heidar (ed), New Knowledge and Changing Circumstances in the Law of the Sea BRILL-Nijhoff, 2020, p. 403. [xxii] Julia Lisztwan, Stability of Maritime Boundary Agreements, 37 Yale Journal of International Law, 2012, p. 191. [xxiii] Convention between the Government of the French Republic and the Government of the Kingdom of Tonga on the Delimitation of EEZ (11 January 1980), available at https://www.un.org/depts/los/LEGISLATIONANDTREATIES/PDFFILES/TREATIES/FRA-TON1980EZ.PDF last accessed August 29, 2022; Minutes of the Meeting between the Delegation of the French Republic and the Delegation of Tuvalu on the Maritime Delimitation (9 December 2014), available at https://www.wallis-et-futuna.gouv.fr/content/download/1261/7756/file/minutestuvalufrance.pdf last accessed August 29, 2022; International Law Association, ‘International Law and Sea-Level Rise’, Sydney Report (2018), p.22. [xxiv] Sarra Sefrioui, ‘Adapting to sea-level rise: a Law of the Sea perspective’ in Gemma Andreone (ed.), The Future of the Law of the Sea, Springer, (2017), p.19 [xxv] In the Matter of the Bay of Bengal Maritime Boundary Arbitration between the People’s Republic of Bangladesh and the Republic of India (Bangladesh v. India), Permanent Court of Arbitration, Award, 7 July 2014, p.63, para.215. [xxvi] Robin Churchill, Vaughan Lowe, Amy Sander, The Law of the Sea (4th edition), Manchester University Press, 2022, p. 368. [xxvii] Treaty between the Federal States of Micronesia and the Republic of the Marshall Islands concerning Maritime Boundaries and Cooperation on related Matters (5 July 2006), available at https://www.un.org/depts/los/LEGISLATIONANDTREATIES/PDFFILES/FSM-RMI.pdf last accessed August 29, 2022. [xxviii] International Law Commission, ‘Sea-Level Rise in relation to international law’, First Issues Paper by Bodgan Aurescu and Nilufer Oral, A/CN.4/740, 2020, p.50, para.134, available at https://documents-dds-ny.un.org/doc/UNDOC/GEN/N20/053/91/PDF/N2005391.pdf?OpenElement last accessed October 28, 2022. [xxix] Ibid, p.51, para.136. [xxx] International Law Commission, ‘Sea-Level Rise in relation to international law’, First Issues Paper by Bodgan Aurescu and Nilufer Oral, A/CN.4/740, 2020, p.50, para.134; International Law Association, ‘International Law and Sea-Level Rise’, Sydney Report (2018), p. 20-22. [xxxi] Alfred Soons, ‘The Effects of a Rising Sea Level on Maritime Limits and Boundaries’, Netherlands international Law Review, vOL37, Issue 2, 1990, p. 229; Vladyslav Lanovoy and Sally O’Donnell, ‘Climate Change and Sea-Level Rise: is the UN Convention on the Law of the Sea Up to the Task?’, International Community Law Review, Vol. 23(4), 2021, pp. 153-154; Tony George Puthucherril, ‘ Rising Seas, Receding Coastlines, and Vanishing Maritime Estates and Territories: Possible Solutions and Reassessing the Role of International Law, International Community Law Review 16(1), 2014, pp. 58-59; Jenny Grote Stoutenburg, Disappearing Island States in International Law, 2015, Martinus Nijhoff, 2015, p. 139 [xxxii] Kya Raina Lal, ‘Legal Measures to Address the Impacts of Climate Change-Induced Sea-Level Rise on Pacific Statehood, Sovereignty, and EEZ’, Auckland University Law Review, Vol. 23, 2017 p.255. [xxxiii] Julia Lisztwan, ‘Stability of Maritime Delimitation Agreements’, 37 Yale Journal of International Law, (2012), p. 185. [xxxiv] Case Concerning the Gabcikovo-Nagymaros Project (Hungary v. Slovakia), Judgment of 25 September 1997, ICJ Reports, p. 31, para.104. [xxxv] UNCLOS, preamble.

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