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Climate Change and Efforts to Stabilise
Otherwise Fluctuating Maritime Entitlements
By Dr Snjólaug Árnadóttir
Maritime limits, maritime boundaries, acquiescence, changing coastlines
States have long fought to extend the limits to their maritime entitlements seaward but sea level
rise and coastal erosion are threatening to push those limits landward. Unilaterally declared
maritime limits generally fluctuate to reflect changes in relevant coastal geography but there
are two exceptions to that rule. Straight baselines at highly unstable, deltaic coastlines and
limits to the continental shelf beyond 200 nautical miles enjoy a distinct level of stability, albeit
only provisional in the case of straight baselines. However, if States continuously rely on duly
published maritime limits as circumstances change, they can potentially achieve acquiescence
for all maritime limits. Furthermore, States can tacitly accept maritime limits through boundary
agreements and such agreements generally remain enforceable, regardless of subsequent
change to relevant coastal geography. The same is true of bilateral boundaries established
through judicial decisions.
This article discusses the options available to States for stabilising maritime limits under
existing law. The aim is to contribute to the ongoing debate concerning legal reform for
Keywords: ........................................................................................................................................... 1
Abstract: .............................................................................................................................................. 1
I. Introduction ......................................................................................................................................... 3
II. Unilateral Declarations Establishing Maritime Limits ....................................................................... 6
A. Normal, Straight and Archipelagic Baselines and Derived Outer Limits ................................... 6
B. Straight Baselines at Highly Unstable Deltaic Coastlines .......................................................... 9
C. Permanently Described Continental Shelf Limits ..................................................................... 10
III. Tacitly Accepted Unilateral Maritime Limits ................................................................................. 12
IV. Agreed or Judicially Settled Maritime Boundaries ......................................................................... 15
V. Conclusion ....................................................................................................................................... 19
Coastal States are entitled to different maritime zones under the United Nations Convention on
the Law of the Sea (UNCLOS)
and they have various rights and obligations within each zone.
For example, States enjoy sovereign rights to explore and exploit all natural resources within
the exclusive economic zone so it generally serves their interests to extend such jurisdiction to
rich fishing grounds and mineral deposits. It is in this quest for expansive sovereign jurisdiction
that States have long sought to extend their maritime claims seaward. This was evident in the
1951 Anglo-Norwegian Fisheries case when Norway defended its right to draw straight
baselines along the furthest extent of the coast
and in the Cod Wars from 1948-1976 when
Iceland fought to expand its fisheries jurisdiction.
International law governing the breadth of
maritime zones and the right to establish straight baselines was clarified in 1982, through the
adoption of UNCLOS. However, the enforceability of these limits is now threatened by new
challenges, not anticipated by UNCLOS; namely, sea level rise and coastal erosion.
The breadth of each maritime zone is measured from baselines (with the exception of the
continental shelf where the natural prolongation of submerged territory extends beyond 200
nautical miles (nm)).
States establish baselines and outer maritime limits through unilateral
acts. If neighbouring States have overlapping claims, bilateral boundaries must be delimited
through agreements or other peaceful means.
These limits and boundaries are established on
the basis of coastal geography
because maritime entitlements are generated by naturally
formed land territory.
More specifically, it is the coastal front that establishes the juridical link
between sovereign territory and maritime entitlements.
Coastal features must satisfy certain conditions to generate, and continuously support, claims
to maritime zones. They only generate entitlements to exclusive economic zones or continental
shelves if they qualify as islands, i.e. are above water at high-tide and sustain human habitation
or economic life.
Coastal features that do not meet these requirements can still generate
territorial sea entitlements, i.e. if they qualify as rocks,
but only if they are above water at
low-tide and less than 12 nm from the nearest island or mainland.
Low-tide elevations that
are situated beyond the breadth of the territorial sea from a mainland or an island generate no
Furthermore, States cannot claim sovereignty over low-tide elevations
United Nations Convention on the Law of the Sea (adopted 10 December 1982, entered into force 16
November 1994) 1833 UNTS 3.
Anglo-Norwegian Fisheries (United Kingdom/Norway) (Judgment)  ICJ Rep 116.
See Guðni Th. Jóhannesson, Þorskastríðin þrjú (Hafréttarstofnun Íslands 2006); Fisheries Jurisdiction (United
Kingdom of Great Britain and Northern Ireland v Iceland) (Merits)  ICJ Rep 3.
UNCLOS article 76.
See UNCLOS articles 15, 74(1), 83(1) and UNCLOS part XV.
See e.g. Land and Maritime Boundary between Cameroon and Nigeria (Cameroon v Nigeria: Equatorial
Guinea intervening) (Judgment)  ICJ Rep 303, para 295; Delimitation of the Continental Shelf between
the United Kingdom of Great Britain and Northern Ireland, and the French Republic (United Kingdom/France)
(Arbitral Award)  RIAA volume XVIII, 3, para 84; North Sea Continental Shelf (Federal Republic of
Germany/Netherlands) (Federal Republic of Germany/Denmark) (Judgment)  ICJ Rep 3, para 96.
See UNCLOS articles 13(1), 60(80) and 121(1); South China Sea (Philippines v China) (Merits) (2016) 170
ILR 1, para 508.
Continental Shelf (Libyan Arab Jamahiriya/Malta) (Judgment)  ICJ Rep 13, 41.
See UNCLOS article 121.
UNCLOS article 121(3).
UNCLOS article 13.
UNCLOS article 13(2).
or submerged land territory.
Conditions to generate maritime claims may be clearly satisfied
when first presented but climate-related changes to the coastline are tearing at the foundations
of such claims and consequently, their enforceability.
Anthropogenic sea level rise hit a new high in the years between 2006-2015, when average,
global sea levels rose by 3.6 mm per year.
The trend is continuing
and sea levels are
expected to rise by up to 0.87 metres worldwide by 2100 if global warming increases by 2°C
from pre-industrialised levels.
Additionally, the instability and melting of ice sheets in the
Polar Regions may cause a further rise of several metres.
Climate change will also exacerbate
coastal erosion, flooding and salinization and these changes threaten all low-lying coasts.
Some areas will experience significant deviations from the average predictions (up to 30%),
making sea level rise, and other climate-related changes (such as extreme weather events),
more severe in those parts of the world.
These changes will affect the living conditions of at
least 300 million people by 2050.
Furthermore, they may lead to loss of maritime
entitlements, and even loss of statehood.
These changes will affect the classification of coastal
features all over the world, reducing islands to rocks, low-tide elevations or fully submerged
features. Moreover, baselines generally fluctuate to reflect changes to relevant coastal
geography de lege lata; they recede landward with receding coastlines and extend seawards in
case of land accretion or the creation of new, naturally formed islands.
Thus, coastal changes
will affect new maritime claims, but not necessarily all pre-existing entitlements.
States have tried to strengthen their maritime claims by reinforcing their coasts and building
artificial islands. Artificial conservation of coastlines is permissible under existing
international law and this method can serve to protect entitlements extending from naturally
South China Sea (n 7) para 309.
IPCC, ‘2019: Summary for Policymakers’ in Hans-Otto Pörtner, Debra Roberts, Valérie Masson-Delmotte,
Panmao Zhai, Melinda Tignor, Elvira Poloczanska, Katja Mintenbeck, Andrés Alegría, Maike Nicolai, Andrew
Okem, Jan Petzold, Bard Rama, Nora Weyer (eds) IPCC Special Report on the Ocean and Cryosphere in a
Changing Climate, para A.3.1.
Ibid, para A.3.2.
IPCC, ‘2018: Summary for Policymakers’ in Valérie Masson-Delmotte, Panmao Zhai, Hans-Otto Pörtner,
Debra Roberts, James Skea, Priyadarshi Shukla, Anna Pirani, Wilfran Moufouma-Okia, Clotilde Péan, Roz
Pidcock, Sarah Connors, J B Robin Matthews, Yang Chen, X Zhou, Melissa Gomis, Elisabeth Lonnoy, Tom
Maycock, Melinda Tignor, and Tim Waterfield (eds) Global Warming of 1.5°C. An IPCC Special Report on the
impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission
pathways, in the context of strengthening the global response to the threat of climate change, sustainable
development, and efforts to eradicate poverty, para B.2.1.
Ibid, para B.2.2.
Michael Oppenheimer and Bruce Glavovic (coordination lead authors) ‘2019: Sea Level Rise and
Implications for Low-Lying Islands, Coasts and Communities’ in IPCC Special Report on the Ocean and
Cryosphere in a Changing Climate (n 14) 324.
IPCC, ‘2019: Summary for Policymakers’ (n 14) para A 3.4.
Scott Kulp and Benjamin Strauss, ‘New elevation data triple estimates of global vulnerability to sea-level rise
and coastal flooding’ (2019) 10 Nature Communications, 1, 3.
Rosemary Rayfuse, ‘Chapter 6: Climate Change and the Law of the Sea’ in Rosemary Rayfuse and Shirley
Scott (eds) International Law in the Era of Climate Change, 147, 152. See also Emily Crawford and Rosemary
Rayfuse ‘Chapter 10: Climate Change and Statehood’ in Rosemary Rayfuse and Shirley Scott (eds) International
Law in the Era of Climate Change, 243, 249.
David D Caron, ‘Climate Change, Sea Level Rise and the Coming Uncertainty in Oceanic Boundaries: A
Proposal to Avoid Conflict’ in Seoung-Yong Hong and Jon M Van Dyke (eds) Maritime Boundary Disputes,
Settlement Processes and the Law of the Sea (Martinus Nijhoff 2008) 1, 2.
However, an international tribunal has ruled that artificial islands cannot
generate maritime entitlements.
Shoreline protection is arguably the most reliable option,
under existing international law, for securing unilateral maritime limits against fluctuations.
Yet, artificial conservation of the coastline is very expensive
and it may be more beneficial
for the global community to invest in climate change mitigation and adaptation activities
instead of preservation of maritime limits.
Leading scholars have put forth proposals to stabilize maritime limits to prevent the fluctuation
of maritime limits.
The International Law Commission (ILC) decided, on 21 May 2019, to
establish an open-ended Study Group on the topic of sea level rise.
The ILC has, at the time
of writing, published one report with preliminary observations of the Study Group’s co-chairs
and issued examples from State practice. The State practice is too disperse to support the
formation of a customary rule but the co-chairs seem open to the possibility of allowing States
to freeze all maritime limits to prevent inequitable consequences of sea level rise.
proposals de lege ferenda would make it possible for States to fix the location of baselines
and/or all outer limits of maritime zones, notwithstanding subsequent changes to relevant
However, these proposals cannot be reconciled with existing international law and
UNCLOS will not be easily changed or superseded.
This article will explore the options that are available to States de lege lata for stabilising
otherwise fluctuating maritime entitlements through (II) unilateral claims, (III) acquiescence
and (IV) bilateral arrangements. Chapter II considers rules governing the establishment of inner
and outer maritime limits through unilateral claims of States and explains to what degree such
limits can be stabilised under existing law. Chapter III explores the legal requirements for
acquiring tacit acceptance of unilateral maritime limits along changing coastlines. Chapter IV
discusses the stability generally afforded to agreed or judicially decided maritime boundaries
and highlights important exceptions. Finally, conclusions are presented in chapter V. Different
scholars have addressed these issues,
so have two committees of the International Law
See Alfred H A Soons, ‘The Effects of a Rising Sea Level on Maritime Limits and Boundaries’ (1990) 37 (2)
Netherlands International Law Review 207, 216-218, 222.
South China Sea (n 7) para 305.
Alfred H A Soons (n 23) 222.
See David D Caron, ‘When Law Makes Climate Change Worse: Rethinking the Law of Baselines in Light of
a Rising Sea Level’ (1990) 17 (4) Ecology Law Quarterly 621, 639-640.
See, e.g., Davor Vidas, David Freestone and Jane McAdam (eds) International Law and Sea Level Rise (Brill
2019) 32; David D Caron, (n 22) 12, 14; Jonathan Lusthaus, ‘Shifting Sands: Sea Level Rise, Maritime
Boundaries and Inter-state Conflict’ (2010) 30 (2) Politics 113, 117; Alfred H A Soons (n 23) 225; Rosemary
Rayfuse, ‘International Law and Disappearing States: Utilising Maritime Entitlements to Overcome the
Statehood Dilemma’ (2010) 52 University of New South Wales Faculty of Law, Research Paper Series, 1, 5-7.
GAOR, ‘Report of the ILC on the Work of its Seventy-First Session’ (29 April-7 June and 8 July-9 August
2019) UN Doc A/74/10, para 265.
ILC, ‘Sea-level rise in relation to international law: First issues paper’ (27 April–5 June and 6 July–7 August
2020) UN Doc A/CN.4/740, see para 104(e) and (f).
See, e.g., ILA Committee on International Law and Sea Level Rise ‘Minutes of the Lopud Intersessional
Meeting’ (ILA 2017) 14.
Robin R Churchill, ‘The Impact of State Practice on the Juridictional Framework Contained in the LOS
Convention’ in Alex G Oude Elferink (ed) Stability and Change in the Law of the Sea: The Role of the Los
Convention (Martinus Nijhoff 2005) 91, 97.
See, e.g., Jenny Grote Stoutenburg, ‘Implementing a New Regime of Stable Maritime Zones to Ensure the
(Economic) Survival of Small Island States Threatened by Sea-Level Rise’ (2016) 26 The International Journal
of Marine and Coastal Law 263; 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) 3; Guifang (Julia) Xue, ‘Climate
Association (ILA), and most recently the International Law Commission (ILC). What sets this
article apart from earlier writings is the emphasis on practical approaches for States to stabilise
the limits to their maritime entitlements and the special attention afforded to acquiescence and
bilateral boundaries, but the latter are often assumed to be immune from change. Furthermore,
this article engages with the very recent preliminary findings of the ILC on the topic of sea
II. Unilateral Declarations Establishing Maritime Limits
The act of establishing baselines is a unilateral act and as such, it only has binding force insofar
as it adheres to international law. Unilateral limits may be lawful when first established but the
submergence of coastal features can necessitate adjustment of baselines and derived maritime
limits to bring them in conformity with the applicable law. Indeed, ‘maritime zones under
coastal State jurisdiction have no legal existence in the absence of a coastal front’
maritime limits are only opposable to other States insofar as they coincide with the governing
States can establish different types of baselines to mark the landward limit to their maritime
entitlements and different types of outer continental shelf limits. These differences are relevant
when evaluating the effects of changing coastal geography, i.e. whether the limits can
withstand subsequent changes to the coastline. The following sections explore possibilities for
stabilising (A) normal, straight and archipelagic baselines and derived limits; (B) straight
baselines at highly unstable coastlines; and (C) permanently described outer continental shelf
A. Normal, Straight and Archipelagic Baselines and Derived Outer Limits
Normal baselines follow the low-water line along relevant coastlines.
Such baselines are
applicable by default, unless otherwise specified.
States can establish straight baselines
‘where the coastline is deeply indented and cut into, or if there is a fringe of islands along the
coast in its immediate vicinity’.
Straight closing lines may also be used to close off bays and
Archipelagic States may use archipelagic baselines where the requirements of
UNCLOS article 47 are satisfied.
Straight and archipelagic baselines are drawn by joining
appropriate basepoints along the coastline. They do not follow the low-water line as closely as
normal baselines but should not depart from the general direction of the coast to ‘any
Change Challenges and the Law of the Sea Response’ in Oliver C Ruppel, Christian Roschmann and Katharina
Ruppel-Schlichting (eds) Climate Change: International Law and Global Governance: Volume I: Legal
Responses and Global Responsibility (Nomos 2013), 549.
The article is partly based on the author’s monograph, Climate Change and Maritime Boundaries: Legal
Consequences of Sea Level Rise (Cambridge University Press 2021).
Geoffrey Marston, ‘The Stability of Land and Sea Boundary Delimitations in International Law’ in Gerald H
Blake (ed), Maritime Boundaries: World Boundaries (Routledge 1994) 144, 154.
Anglo-Norwegian Fisheries (United Kingdom/Norway) (Judgment)  ICJ Rep 116, 132.
UNCLOS article 5.
Robert Beckman and Clive Schofield, ‘Moving Beyond Disputes Over Island Sovereignty: ICJ Decision Sets
Stage for Maritime Boundary Delimitation in the Singapore Strait’ (2009) 40 (10) Ocean Development and
International Law 1, 5.
UNCLOS article 7.
See UNCLOS arties 9 and 10.
UNCLOS article 47.
States must take positive action to activate the right to employ straight
or archipelagic baselines and these baselines must be clearly defined by relevant coastal States.
Outer maritime limits to maritime zones are generally at a fixed distance from baselines and
can, consequently, be identified by reference to baselines. However, the outer limits of the
continental shelf can be determined by reference to the natural prolongation of the continental
margin where it extends beyond 200 nm.
UNCLOS article 16 provides that straight baselines,
closing lines around bays and rivers, and the outer limits derived therefrom ‘shall be shown on
charts of a scale or scales adequate for ascertaining their position. Alternatively, a list of
geographical coordinates of points, specifying the geodetic datum, may be substituted’.
Moreover, coastal States must duly publicise their charts or lists of geographical coordinates
and deposit copies with the UN Secretary-General (UNSG).
The same applies to archipelagic
and articles 75 and 84 further confirm that these obligations extend to the outer
limits of the exclusive economic zone and the continental shelf.
The impacts of climate change on maritime entitlements are most severe when they change the
status of coastal features. A low-tide elevation may only be used to form the baseline for
measuring the breadth of the territorial sea if it is within 12 nm from the mainland or an island.
Furthermore, islands that become uninhabitable or incapable of sustaining economic life
because of inundation will no longer generate an exclusive economic zone or a continental
shelf, i.e. if they are reduced to rocks as per UNCLOS article 121(3), and if a rock is completely
submerged it also loses all entitlements to a territorial sea.
Similarly, States can lose the
capacity to qualify as archipelagic States and, consequently, the right to rely on straight
The gradient of the coast can be an important factor for evaluating the consequences of coastal
changes for maritime entitlements. ‘[W]here the coastline is gently shelving, even relatively
slight changes in sea level vertically can result in significant shifts in the location of the low-
water line horizontally and this, in turn, can have significant impacts on the spatial extent of
national maritime claims.’
Straight baselines, archipelagic baselines and closing lines do not
have the same direct correlation to the low-water line as normal baselines; the mean low-water
line can undergo substantial changes without affecting the furthest seaward extensions, which
the basepoints for closing lines, archipelagic and straight baselines rely on. If basepoints are on
elevated peaks they may withstand coastal erosion and sea level rise, effectively making
coastlines more heavily indented but without shifting the location of straight baselines or
UNCLOS does not explicitly state that baselines and derived outer limits must fluctuate in
accordance with changing coastlines. Most commentators adhere to the theory of ambulatory
baselines and this is clearly reflected in the work of the ILA Baselines Committee and the ILA
UNCLOS articles 7 and 47.
See section II.B. and UNCLOS article 76.
UNCLOS article 16.
See UNCLOS articles 47(8) and (9).
UNCLOS article 13.
Alfred H A Soons (n 27) 216-217.
See UNCLOS article 47.
Clive Schofield and Robin Warner, Climate change and the oceans gauging the legal and policy currents in
the Asia Pacific and beyond (Edward Elgar Pub 2012) 136.
Committee on International Law and Sea Level Rise.
However, Purcell argues that baselines
do not necessarily fluctuate with changing coastlines because the rules regarding the extent of
baselines are separate from the entitlement to a lawfully established claim.
She seems to view
the rules on maritime limits as constitutive and not requiring ongoing adherence.
The theory of ambulatory baselines has been derived from two exceptions, which are enshrined
in UNCLOS articles 7(2) and 76(9). The theory provides that ‘baselines and boundaries
generated from them are “ambulatory” […] that is, the baselines – and therefore the boundaries
– adjust themselves to a changing coastline’.
UNCLOS article 7(2) provides that straight
baselines at highly unstable deltaic coastlines remain effective ‘notwithstanding subsequent
regression of the low-water line […] until changed by the coastal State in accordance with this
Convention’. UNCLOS article 76(8) allows States to establish ‘final and binding’ outer limits
to the continental shelf beyond 200 nm and these are permanently described in accordance with
UNCLOS article 76(9). This stability is only afforded to straight baselines and outer continental
shelf limits in very specific circumstances and it is contingent on different procedural
requirements. Therefore, the general rule is that all limits fluctuate in accordance with changing
coastal geography. Straight baselines, and derived outer limits, can remain enforceable as
coastlines change but only if the instability is a result of a delta and other natural conditions or
if the limits conform to information submitted to the UNSG, as per UNCLOS article 16.
Similarly, continental shelf limits can remain stable but only if established on the basis of
recommendations of the Commission on the Limits of the Continental Shelf (CLCS) and if the
limits have been permanently described before the UNSG.
Many States fail to submit relevant data to the UNSG. Some States adopt legislation
concerning their limits but according to the UN Division for Ocean Affairs and the Law of
the Sea (DOALOS), such acts do not suffice to satisfy obligations arising under UNCLOS
articles 16(2), 47(9), 75(2), 76(9) and 84(2): ‘The mere existence or adoption of legislation or
the conclusion of a maritime boundary delimitation treaty registered with the Secretariat,
even if they contain charts or lists of coordinates, cannot be interpreted as an act of deposit
with the UNSG under the Convention.’
In Nicaragua v Colombia, the ICJ referred to
Nicaragua’s failure to notify the UNSG of the location of base points, in accordance with
UNCLOS article 16(2) and found that, for that reason, the relevant area would have to be
‘determined only on an approximate basis’.
Therefore, it may be concluded that failure to
deposit charts and coordinates with the UNSG affects the right to rely upon certain maritime
Baselines, and derived outer limits (with the exception of the outer limits of the continental
shelf), will shift either automatically in accordance with physical changes to coastlines or
ILA Baselines Committee ‘Conference Report Sofia 2012’ (ILA 2012) 31; ILA Committee on International
Law and Sea Level Rise ‘Sydney Conference’ (ILA 2018) 11-12.
Kate Purcell, Geographical Change and the Law of the Sea (Oxford University Press 2019) 12-13.
David D Caron, (n 22) 2.
See UNCLOS articles 76(8) and (9).
DOALOS ‘Deposit of charts and/or lists of geographical coordinates and DOALOS Geographic Information
System (GIS)’ (United Nations 2016) available at:
https://www.un.org/depts/los/doalos_activities/about_doalos.htm accessed 20 January 2021.
Territorial and Maritime Dispute (Nicaragua v Colombia) (Judgment)  ICJ Rep 624, para 35 and Award
in the arbitration regarding the delimitation of the maritime boundary between Guyana and Suriname (Guyana v
Suriname) (2007) XXX RIAA 1, para 159.
through mandatory adjustments enacted by coastal States.
Coastal States have an obligation
to display maritime limits on charts or lists of coordinates and even though there is no explicit
obligation to submit such data regarding the normal baseline to the UNSG, UNCLOS article 5
clearly assumes that normal baselines are displayed on officially recognised charts. UNCLOS
provisions concerning the entitlement to maritime zones, breadth of maritime zones and
obligation to display maritime limits apply on a continuing basis and, therefore, there must be
an obligation to reflect changes to ambulatory limits on relevant charts. Inaction may lead to
de facto stable limits but only tentative stability because limits can always be challenged by
other States if not in conformity with the applicable law. When challenged and if the charted
line proves inaccurate, courts and tribunals resort to the actual low-water line.
According to this, unilaterally declared maritime limits usually become unenforceable when
essential coastal geography changes. However, States can rely on outdated maritime limits and
hope they go unchallenged, which can even lead to tacit acceptance as explained in section III.
Yet, this comes at the risk of falling back to the mean low-water line,
in which case a moderate
claim to straight or archipelagic baselines in light of the changed coastline would be more
beneficial for the coastal State.
B. Straight Baselines at Highly Unstable Deltaic Coastlines
UNCLOS article 7(2) forms an exception to the general rule that all baselines become
unopposable as soon as they cease to satisfy the requirements essential for their establishment.
However, the stability afforded to straight baselines at highly unstable deltaic coastlines seems
to be provisional.
UNCLOS article 7(2) provides that:
Where because of the presence of a delta and other natural conditions the coastline is
highly unstable, the appropriate points may be selected along the furthest seaward
extent of the low-water line and, notwithstanding subsequent regression of the low-
water line, the straight baselines shall remain effective until changed by the coastal
State in accordance with this Convention.
The phrase ‘until changed by the coastal State in accordance with this Convention’ suggests
that States, relying on straight baselines along highly unstable coastlines, are under an
obligation to adjust such baselines when coastlines change. As explained by Soons, this
reference to subsequent change indicates that States do not have discretionary powers in this
Likewise, Churchill and Lowe have asserted that ‘article 7(2) does, of course, require
a State eventually to change its baselines’.
Indeed, it seems unlikely that States would ever
update straight baselines, following the regression of the low-water line, unless they were
obligated to do so.
David D Caron, (n 22) 9.
See Nicaragua v Colombia (n 54) para 35 and Award in the arbitration regarding the delimitation of the
maritime boundary between Guyana and Suriname (Guyana v Suriname) (2007) XXX RIAA 1, para 396.
UNCLOS article 5 is generally understood as referring to ‘the mean low-water line along the coast’. See
Ashley Roach and Robert W Smith, ‘Straight Baselines: The Need for a Universally Applied Norm’ (2000) 31
Ocean Development and International Law 47, 50.
Alfred H A Soons (n 27) 220.
Robin R Churchill and Alan V Lowe, The Law of the Sea, 3rd edition (Juris Publishing 1999) 38.
UNCLOS article 7(2) applies to coastlines that are unstable due to deltas and other natural
conditions and the reference to ‘other natural conditions’ might be interpreted so as to include
instability resulting from sea level rise and other foreseeable changes. Such an approach has
been promoted as a method for stabilizing otherwise ambulatory maritime limits.
noted that the precise scope of UNCLOS article 7(2) is unclear because the provision does not
settle ‘[w]hat degree of change over what period of time would be considered to constitute a
high degree of instability’.
UNCLOS article 7(2) was meant to be a narrow exception,
designed to deal with the exceptional circumstances at the Bengal delta
and not large-scale
changes to coastal geography, such as the complete submergence of islands. Yet, the provision
is not explicitly limited to such circumstances so it might conceivably be used to afford stability
to coastlines affected by sea level rise. Still, the co-chairs of the ILC’s Study Group on sea
level rise have considered this possibility and concluded that it cannot prevent the destabilising
effects of substantial sea level rise.
C. Permanently Described Continental Shelf Limits
Whereas all other maritime limits are established unilaterally by the coastal State, limits to the
continental shelf beyond 200 nm can be permanently established through cooperation with an
international body. UNCLOS article 76(8) provides that ‘[i]nformation on the limits of the
continental shelf beyond 200 nautical miles from the baselines from which the breadth of the
territorial sea is measured shall be submitted by the coastal State to the [CLCS]’. In turn, the
CLCS makes recommendations relating to the establishment of the outer continental shelf
limits and ‘limits of the shelf established by a coastal State on the basis of these
recommendations shall be final and binding.’
Furthermore, coastal States ‘shall’, according
to UNCLOS article 76(9), ‘deposit with the [UNSG] charts and relevant information, including
geodetic data, permanently describing the outer limits of its continental shelf’ and the UNSG
gives ‘due publicity thereto’.
The International Tribunal for the Law of the Sea (ITLOS) has confirmed that the significance
of the outer continental shelf limits being final and binding is that it enhances ‘opposability
with regard to other States’.
ITLOS also noted, in Bangladesh/Myanmar, that the continental
shelf limits beyond 200 nm are opposable to third States, despite being based on unilateral acts,
as long as they are compliant with UNCLOS article 76 and the recommendations of the
It is not entirely clear whether all continental shelf limits may be permanently described or
whether the exception only applies to the final and binding limits beyond 200 nm. A reading
of UNCLOS article 76(9) in conjunction with article 76(8) supports the conclusion that the
stability is only afforded to limits beyond 200 nm. A majority of scholars endorses this
Moritaka Hayashi ‘Sea Level Rise and the Law of the Sea: Legal and Policy Options’ in Proceedings of
International Symposium on Islands and Oceans (Ocean Policy Research Foundation 2009) 79.
ILA Baselines Committee, ‘Conference Report Washington 2014’ (ILA 2014) referring to Edward Duncan
Brown, The International Law of the Sea, vol I (Dartmouth 1994) 27.
See Bay of Bengal Maritime Boundary Arbitration (Bangladesh v India) (2014) 167 ILR 1, para 237 referring
to hearing transcript, 117, paras 1 and 16.
UN Doc A/CN.4/740 (n 29) para 79.
UNCLOS article 76(8).
Bangladesh/Myanmar (n 62) para 407.
The alternative would render UNCLOS article 84 (obligating States to describe
continental shelf limits to the UNSG) redundant.
Continental shelf limits can fluctuate until they are permanently described and States cannot
establish final and binding continental shelf limits without the recommendations of the CLCS.
Therefore, there is a matter of urgency in acquiring CLCS recommendations, particularly
where coastlines are receding. Article 4 of UNCLOS Annex II provides that in order to receive
recommendations from the CLCS, States must submit relevant data to the commission ‘as soon
as possible but in any case, within 10 years of the entry into force of this Convention for that
State.’ The earliest deadline for submitting relevant data to the CLCS was, therefore, 16
November 2004, ten years after the entry into force of UNCLOS for the first States Parties.
However, this process proved more arduous than originally expected
and the deadline was
postponed to 13 May 2009. This meant that the earliest date would be 13 May 2009 and that
for those States that became bound by UNCLOS after 13 May 1999, the deadline would still
be ten years after the entry into force of the Convention for that State.
Due to these
complications, States Parties also concluded that preliminary submissions would suffice to halt
the 10-year deadline for submissions.
Article 4 of UNCLOS Annex II is not clear in regard to potential consequences for non-
compliance with the 10-year deadline. Oude Elferink has argued that States might either be
barred from submitting their data to the CLCS after their deadline expires or that the CLCS
would not be obligated to consider any submissions after that time.
However, this view is not
widely held and according to Judge Heiðar, ‘there is no sanction for failure to make a
submission within [the 10-year] period’.
At the time of writing, 88 submissions have been made to the CLCS and the CLCS has
produced 35 recommendations.
The CLCS is expected to need a couple of decades to go
through all the submissions lodged with it so far.
Thus, it remains to be seen whether all the
ILA Committee on the Outer Continental Shelf ‘Conference Report Toronto 2006’ (ILA 2006) 16.
UNCLOS article 76(8), see also Maritime Delimitation in the Indian Ocean (Somalia v Kenya) (Preliminary
Objections)  ICJ Rep 1, para 66; Questions of the Delimitation of the Continental Shelf Between
Nicaragua and Colombia Beyond 200 Nautical Miles from the Nicaraguan Coast (Nicaragua v Colombia)
(Preliminary Objections)  ICJ Rep 1, paras 107-108.
This was particularly difficult for certain developing States, see Somalia v Kenya (n 68) para 17.
UNCLOS: Meeting of States Parties ‘Decision regarding the date of commencement of the ten-year period for
making submissions to the Commission on the Limits of the Continental Shelf set out in article 4 of Annex II to
the United Nations Convention on the Law of the Sea’ (29 May 2001) UN Doc SPLOS/72.
See UNCLOS: Meeting of States Parties ‘Decision regarding the workload of the [CLCS] and the ability of
States, particularly developing States, to fulfil the requirements of article 4 of Annex II to the Convention, as
well as the decision contained in SPLOS/72, paragraph (a)’ (20 June 2008) UN Doc SPLOS/183.
Alex G Oude Elferink, ‘Article 76 of the LOSC on the Definition of the Continental Shelf: Questions
concerning its Interpretation from a Legal Perspective’ (2006) 21 (3) The International Journal of Marine and
Coastal Law 269, 279.
Tómas H Heiðar, ‘Legal Aspects of Continental Shelf Limits’, in Myron H Nordquist, John Norton Moore
and Tómas H Heiðar (eds) Legal and Scientific Aspects of Continental Shelf Limits (Martinus Nijhoff 2004) 19,
DOALOS ‘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’ (UN 2021) available at:
https://www.un.org/Depts/los/clcs_new/commission_submissions.htm accessed 16 January 2021.
Alex G Oude Elferink, ‘The Continental Shelf in the Polar Regions: Cold War or Black-Letter Law?’ (2009)
40 Netherlands Yearbook of International Law 121, 133.
States that have made submissions to the CLCS will ever acquire stable outer limits to
continental shelves extending more than 200 nm from baselines. In the meantime, some islands
that currently generate an entitlement to a continental shelf may be reduced to rocks, incapable
of sustaining human habitation or economic life, low-tide elevations or fully submerged
features. That might lead the CLCS to request further, contemporaneous evidence, and
recommend final and binding continental shelf limits excluding entitlements previously
generated by the submerged territory.
It should also be noted that certain States do not have sufficient resources to collect the
necessary data and make submissions to the CLCS in order to establish permanent continental
Furthermore, it seems that non-Parties may be precluded from submitting their
data to the CLCS and establishing final and binding limits on that basis. This is not explicitly
dealt with in UNCLOS but in Judge Heiðar’s opinion non-Parties have no such right under
UNCLOS or customary international law.
One of the arguments supporting this conclusion
is that UNCLOS article 82, concerning revenue sharing and contributions to the International
Seabed Authority, only applies to States Parties. If States Parties alone carry these obligations
(relating to the outer continental shelf beyond 200 nm), it seems prudent that they would be the
only ones benefitting from final and binding continental shelf limits beyond 200 nm.
The International Court of Justice (ICJ) has explained that States Parties to UNCLOS are
obligated to submit relevant data to the CLCS ‘whereas the making of a recommendation,
following examination of that information, is a prerogative of the CLCS’.
certainly have no obligation to make submissions to the CLCS but this does not preclude the
possibility of them submitting their data to the CLCS. However, they would always be
dependent on the CLCS’s decision to make a recommendation and probably be placed at the
end of a long line. Consequently, not all States will be able to acquire final and binding outer
continental shelf limits but to increase their chances, States are advised to ratify UNCLOS and
submit relevant data to the CLCS in a timely fashion.
III. Tacitly Accepted Unilateral Maritime Limits
As has been noted above, unilateral limits are generally not opposable to other States unless
and insofar as they delineate entitlements afforded to coastal States under the applicable
international law. This is why unilateral limits must be adjusted to changing coastlines to
continuously meet relevant requirements. Yet, unilaterally established maritime limits do not
automatically cease to exist if they are inconsistent with international law. On the contrary,
States can continuously rely on excessive maritime limits if they go unchallenged.
The co-chairs of the ILC’s Study Group on sea level rise have suggested that States might be
able to continuously rely on duly published maritime limits, notwithstanding subsequent
changes to relevant coasts. They suggest, in their preliminary findings, that this might be
achieved through revised interpretation of UNCLOS. The co-chairs clearly differentiate
between maritime limits that have been given due publicity with submission of data to the
UNSG, and those that have not.
They suggest that UNCLOS might be interpreted in such a
Tómas H Heiðar (n 73) 31.
Questions of the Delimitation of the Continental Shelf Between Nicaragua and Colombia Beyond 200
Nautical Miles from the Nicaraguan Coast (n 68) para 107.
UN Doc A/CN.4/740 (n 29) para 143.
way as to allow all States to freeze their maritime limits by depositing information on the limits
with the UNSG and not updating such notifications to reflect receding coastlines.
entail a departure from the current interpretation of UNCLOS, which might be possible under
article 31(3) of the Vienna Convention on the Law of Treaties, but only if supported by
consistent State practice.
Several States have informed the ILC of relevant practice in this
regard and that demonstrates a broad understanding of the ambulatory nature of maritime
but also, efforts by particularly affected States (the Pacific small island developing
States) to change the interpretation.
The ILC’s preliminary findings on the topic of ambulatory maritime limits is that it would be
feasible to stabilise maritime entitlements.
It might threaten legal stability and undermine
UNCLOS if States were encouraged to reinterpret the convention and a consensus on the issue
seems like a distant possibility. Another option would be to encourage tacit acceptance of
outdated maritime limits. This might achieve the same objective, without interfering directly
with the interpretation of UNCLOS. Also, it might provide a useful degree of flexibility. After
all, Pacific island States seem more interested in fixing all maritime limits than the United
Kingdom and the United States, for example, and principles of equity would support the notion
that vulnerable States enjoy flexibility. However, it would be difficult to reconcile regional
differences in the interpretation or application of UNCLOS.
Maritime limits can be tacitly accepted in a legally binding manner. This can make them
enforceable against other States, even if they do not conform to the maritime entitlements
afforded to States under UNCLOS, or consonant customary international law. This process is
called acquiescence and it demonstrates ‘tacit recognition manifested by unilateral conduct
which the other party may interpret as consent’.
Although consent-based, the relationship
established through acquiescence ‘between the author State and the addressee or addressees
[…] is distinct from a treaty relationship’.
The ILC has published ‘Guiding Principles applicable to unilateral declarations of States
capable of creating legal obligations’.
The principles deal with declarations ‘formulated by
States in exercise of their freedom to act on the international plane’ and not on ‘unilateral acts
[…] formulated in the framework and on the basis of an express authorization under
Thus, the principles are not directly applicable to maritime limits
established in accordance with UNCLOS but the ILC’s commentary and preparatory work is
of relevance for this discussion, particularly to limits that become inconsistent with the law due
to environmental changes. According to Guiding Principle 3, the legal effects of unilateral
Ibid, para 104(e) and (f).
Note that the ‘possibility of amending or modifying a treaty by subsequent practice of the parties has not been
generally recognized’: GAOR, ‘Report of the International Law Commission, Sixty-eighth session’ (2 May-10
June and 4 July-12 August 2016) UN Doc A/71/10, 118, 122.
See UN Doc A/CN.4/740 (n 29) paras 87-88.
Ibid paras 84-86.
Ibid para 190.
Delimitation of the Maritime Boundary in the Gulf of Maine Area (Canada/United States of America)
(Judgment)  ICJ Rep 246, para 130.
ILC, ‘Ninth report on unilateral acts of States’ (6 April 2006) UN Doc A/CN.4/569 and Add.1, para 128.
ILC, ‘Report of the Commission to the General Assembly on the work of its fifty-eighth session’ (1 May-9
June and 3 July-11 August 2006) UN Doc A/CN.4/SER.A/2006/Add.1 (Part 2), para 176.
Ibid para 174.
declarations depend inter alia on the reactions they invoke.
When preparing this Guiding
Principle, the ILC referenced the 1945 Truman proclamation,
whereby the United States
established unilateral limits to the continental shelf. This occurred before the conclusion of a
framework treaty (UNCLOS and the Convention on the Continental Shelf).
declaration soon became opposable because of the positive reactions it received from other
As noted by the ICJ, the Truman proclamation is a ‘particular source that has secured
a general following’.
The ILC also explained how objections could prevent tacit acceptance of maritime limits and
referenced the following example. Turkmenistan established baselines and territorial sea limits
in 1993 and Russia protested these limits in January 1994 by means of a diplomatic note, stating
that this unilateral action would not be recognised by Russia.
According to the ILC, these
protests were ‘necessary to prevent a situation whereby silence on the part of the Russian
Federation could be invoked against it in the future as a tacit acceptance of or acquiescence in
the claims of Turkmenistan’.
Indeed, failure to object to potentially unlawful maritime limits
can amount to acquiescence or tacit acceptance.
Such failure can give unilateral maritime
claims binding force, whereas a successful challenge would make them unenforceable. Guiding
Principle 9 confirms that while ‘[n]o obligation may result for other States from the unilateral
declaration of a State […] the other State or States concerned may incur obligations in relation
to such a unilateral declaration to the extent that they clearly accepted such a declaration’.
States generally have a legal interest in making sure that maritime limits of other States satisfy
the requirements of UNCLOS. Even if they have no overlapping claims to maritime zones,
they may have legitimate interests relating to claims encroaching upon the high seas or the
international seabed area.
On the other hand, it is in the interest of coastal States to push their
maritime limits seaward and some States have gone to great lengths to further their maritime
entitlements. For example, ‘almost all of the States of the Asia-Pacific region have adopted
straight baseline systems that are inconsistent with international law’ and they maintain these
claims despite vigorous opposition.
The ILA Baselines Committee identified 82 protests or
objections to straight baselines. These challenges have been submitted by 21 States and the EU
and lodged against 39 States, covering almost 50% of all straight baseline claims.
States has actively objected to the unlawful use of baselines worldwide and other States have
Ibid para 176.
Harry S Truman, ‘150 - Proclamation 2667 - Policy of the United States with Respect to the Natural
Resources of the Subsoil and Sea Bed of the Continental Shelf’ September 28, 1945.
Convention on the Continental Shelf (adopted 29 April 1958, entered into force 10 June 1964) 499 UNTS
ILC, ‘Eighth report on unilateral acts of States, by Mr. Víctor Rodríguez Cedeño, Special Rapporteur’ (26
May 2005) UN Doc A/CN.4/557, paras 131-133.
North Sea Continental Shelf (n 6) para 100.
UN Doc A/CN.4/557 (n 92) paras 85-88.
Ibid para 94.
Julia Lisztwan, ‘Stability of maritime boundary agreements’ (2012) 37 Yale Journal of International Law 153,
See, e.g., Chagos Marine Protected Area (Mauritius v United Kingdom) (2015) XXXI RIAA 359, para 153;
Anglo-Norwegian Fisheries (n 35) 125.
Ashley Roach and Robert W Smith (n 57) 66.
ILA Baselines Committee, ‘Johannesburg Conference’ (ILA 2016) 17, para 65.
made similar efforts.
These objections can prevent acquiescence because, if successfully
challenged, unlawful maritime limits become invalid vis-à-vis other States.
If States fail to challenge excessive maritime limits, they may later be estopped from
challenging such limits. As explained by Churchill and Lowe:
Where a baseline is clearly contrary to international law, it will not be valid, certainly
in respect of States which have objected to it, though a State which has accepted the
baseline (for example in a boundary treaty) might be stopped from later denying its
validity. In border-line cases—for example, where there is doubt as to whether a State’s
straight baseline system conforms to all the criteria laid down in customary and
conventional law—the attitude of other States in acquiescing in or objecting to the
baseline is likely to prove crucial in determining its validity.
The submission of charts, or lists of geographic coordinates, to the UNSG is crucial for the
formation of acquiescence and estoppel because it provides States with the information
necessary to raise their objections. The ICJ has indicated that challenges should generally be
raised shortly after submission of data to the UNSG, or earlier, to avoid acquiescence. In the
Black Sea case, the Court deemed a basepoint on the seaward end of Sulina dyke to be irrelevant
for the delimitation of a bilateral boundary.
Yet, the decision had no effect on the validity of
Romania’s baselines, which gave that same base point full effect. This was partly due to the
fact that Romania had submitted its data, designating a base point on Sulina dyke, to the UNSG,
in accordance with UNCLOS article 16(2), and Ukraine had raised no objections.
States may be able to prevent acquiescence to excessive maritime limits by challenging them
soon after they are given due publicity in accordance with UNCLOS articles 16(2) and 76(9).
However, the grounds for a challenge may arise years later, when coastal geography
undergoes significant changes, for example with the submergence of an island. States have no
reason to object to lawful maritime limits, but they must be allowed to challenge duly
established limits when they become inconsistent with UNCLOS. After all, ‘[r]ights which
have been acquired in clear conformity with existing law have no need of the doctrine
of acquiescence to confirm their validity’.
It should be noted that it may be difficult to
define the point in time when maritime limits become inconsistent with international law. The
status of coastal features is surveyed and depicted on navigational charts and the
disappearance of a coastal features from such charts could give rise to challenges. However,
the loss of capacity to sustain human habitation and economic life will not be as readily
IV. Agreed or Judicially Settled Maritime Boundaries
In cases where claims of two States to maritime zones overlap, the States are obligated to
establish bilateral boundaries.
This obligation cannot be satisfied through unilateral action.
Ashley Roach and Robert W Smith (n 57) 48.
See, e.g., South China Sea (n 7) paras 278 and 1203 B.(2).
Robin R Churchill and Alan V Lowe, The Law of the Sea, 2nd revised edition (Manchester University Press
Maritime Delimitation in the Black Sea (Romania v Ukraine) (Judgment)  ICJ Rep 61, para 217.
Ian C MacGibbon, ‘The scope of acquiescence in international law’ (1954) 31 British Yearbook of
International Law, 143, 143.
UNCLOS articles 15, 74 and 83.
The States concerned must negotiate the establishment of bilateral boundaries in good faith
‘with the genuine intention of achieving a positive result’.
If States cannot reach an
agreement for the establishment of bilateral boundaries, they can resort to the dispute
settlement mechanisms provided for in UNCLOS Part XV, including judicial settlement.
Consequently, the requirement to establish an agreed boundary can be satisfied by submitting
a boundary dispute to a court or a tribunal.
While unilateral limits are only opposable to other States as long as they satisfy the
requirements of UNCLOS or acquiescence, bilateral boundaries create binding arrangements
subject to pacta sunt servanda
or res judicata.
The binding nature is rooted in consent.
Bilateral boundaries cannot be challenged in the same manner as unilateral limits when
circumstances change; they are generally stable and immune to coastal changes, unless
otherwise agreed. Still, unilateral limits can fluctuate within these binding boundaries unless
specifically agreed upon, tacitly accepted, or permanently described in accordance with
UNCLOS article 76.
Overlapping territorial sea entitlements are delimited through the equidistance method,
establishing boundaries that are equally distant from baselines along adjacent or opposite
coasts, unless a different arrangement is justified by agreement, historic title or special
Boundaries to the exclusive economic zone and continental shelf are
delimited on the basis of international law to achieve equitable solutions.
are available for delimitation of such boundaries but coastal geography is always of pivotal
importance. International courts and tribunals have confirmed this on several occasions.
size of coastal features and their distance from the mainland can be decisive in the delimitation
but these factors can undergo significant changes as sea levels rise and coastlines
States may agree to revise maritime boundaries, whether established by agreements or judicial
decisions. The consent to revise settled boundaries can flow from the terms of the original
agreement or a subsequent agreement. Mutual revision of maritime boundaries naturally
requires the consent of all relevant parties and a State suffering from loss of territory will not
be easily persuaded to construct a new maritime boundary when there is no legal obligation to
do so. However, fundamental changes to coastal geography may justify revision or termination
of bilateral maritime boundaries, despite the objection of one or more parties to the dispute.
The principle of pacta sunt servanda does not provide that all agreements remain inviolable
until the end of time.
On the contrary, States can be released from treaty obligations through
Delimitation of the Maritime Boundary in the Gulf of Maine Area (n 85) para 112(1).
United Nations, Handbook on the Delimitation of Maritime Boundaries (UN 2001) 1.
Frontier Dispute (Burkina Faso v Republic of Mali) (Judgment)  ICJ Rep 554, 577, para 46.
Territorial and Maritime Dispute (Nicaragua v Colombia) (Application by Honduras for Permission to
Intervene)  ICJ Rep 348, 368, para 67.
UNCLOS article 15.
UNCLOS articles 74 and 83.
See e.g. United Kingdom/France (n 6), para 84; North Sea Continental Shelf (n 6), para 96; Cameroon v
Nigeria: Equatorial Guinea intervening (n 6), para 295; Delimitation of the Exclusive Economic Zone and the
Continental Shelf (Barbados v Trinidad and Tobago) (Arbitral Award)  RIAA volume XXVII, 147, para
288 and Continental Shelf (Tunisia/Libyan Arab Jamahiriya) (Judgment)  ICJ Rep 18, para 126.
See e.g. Nicaragua v Colombia (n 56) para 202.
Rein Müllerson, ‘The ABM Treaty: Changed Circumstances, Extraordinary Events, Supreme Interests and
International Law’ (2001) 50 International and Comparative Law Quarterly 509, 525.
peaceful means under the doctrine of rebus sic stantibus, when circumstances leading to the
conclusion of a treaty have changed and obligations under a treaty have become ‘unduly
Similarly, decisions of the ICJ may be revised in light of new facts or
Furthermore, maritime boundaries may be set aside when subject
to the pacta tertiis principle, i.e., when they violate the rights of third States.
possibilities may be available in exceptional circumstances but the general rule remains that
bilateral boundaries are permanently binding.
Rebus sic stantibus provides that an unforeseen fundamental change of circumstance can be
invoked as grounds for suspending, withdrawing from or terminating a treaty if it affects the
essential basis of the treaty and radically transforms obligations still to be performed.
customary rule has been codified in article 62 of the Vienna Convention on the Law of Treaties
(VCLT). The VCLT is limited to treaties between States
that are in written form and
governed by international law.
Yet, the principle may also affect judicial decisions because
res judicata only prevents the revision of boundaries insofar as the same relief is sought on the
grounds advanced in previous proceedings between the same parties.
A fundamental change under article 62 must relate to the facts that led both parties to give their
consent to be bound by the treaty and be extensive enough to alter the treaty’s raison d’être.
Environmental changes affecting coastal geography can potentially qualify as such
affect the essential basis of maritime boundary treaties, given the importance of coastal
geography to the delimitation process. However, changes cannot be invoked to terminate a
treaty if they were foreseen by the parties when the treaty was concluded,
i.e. anticipated in
any way, either expressly or by implied terms.
VCLT article 62(1)(b) provides that the effect
of a change must be to radically transform the extent of obligations still to be performed under
a treaty. An obligation is transformed when it is made more onerous or ‘the value to be gained
by further performance is diminished’.
The reference to obligations still to be performed
confirms that VCLT article 62 is not applicable to treaties that have been fully executed; there
have to be obligations that have not yet been performed or a requirement of continuing
Obligations under a maritime boundary agreement certainly entail ongoing
obligations and the ‘value to be gained by further performance’ will be affected when there is
See Eric Stein and Dominique Carreau, ‘Law and Peaceful Change in a Subsystem: “Withdrawal” of France
from the North Atlantic Treaty Organisation’ (1968) 62 American Journal of International Law 577, 617.
See article 61 of the Statute of the ICJ.
See VCLT article 34.
See VCLT article 62(1).
VCLT article 1.
VCLT article 2(1)(a).
Andreas Kulick, ‘Article 60 ICJ Statute, Interpretation Proceedings, and the Competing Concepts of Res
Judicata’ (2015) 28 (1) Leiden Journal of International Law 73, 74.
Paul Reuter, Introduction to the Law of Treaties (Kegan Paul International 1995) 189.
See Jeremy Waldron, ‘F.W. Guest Memorial Lecture: August 22nd, 2005: The Half-Life of Treaties:
Waitangi, Rebus Sic Stantibus’ (2006) 11 Otago Law Review 161, 170.
VCLT article 62(1).
ILC, ‘Second Report on the Law of Treaties, by Mr GG Fitzmaurice, Special Rapporteur’ (15 March 1957)
UN Doc A/CN.4/107, 33.
Thomas Giegerich, ‘Article 62. Fundamental Change of Circumstances’, in Oliver Dörr and Kirsten
Schmalenbach (eds) Vienna Convention on the Law of Treaties: A Commentary (Springer 2012)1067, 1089,
referring to Yearbook of the ILC, 1957, vol II (n 126) 60, para 151.
ILC, ‘Fifth Report on the Law of Treaties by Sir Humphrey Waldock, Special Rapporteur’ (15 November
1965-18 January 1966) UN Doc A/CN.4/183 and Add.1-4, 43.
a considerable divergence between a State‘s entitlements under UNCLOS and rights afforded
by the agreement.
Even if all the conditions of rebus sic stantibus are met, it is still unlikely that States will be
released from their obligation to respect bilateral maritime boundaries on these grounds. First,
international courts and tribunals have yet to accept the application of the rebus sic stantibus
principle in a contentious case. Second, treaties establishing boundaries are exempt from
termination under VCLT article 62.
This exclusion of boundary treaties may not cover all
maritime boundaries. The ICJ has suggested that treaties delimiting the continental shelf should
fall within this boundary exclusion.
However, the fact that a line qualifies as a boundary in
some respects, does not automatically make it a boundary within the meaning of VCLT article
When codifying the Vienna Convention on the Law of Treaties Between States and
International Organizations or Between International Organizations, the ILC stated that
territorial sea boundaries were ‘true limit[s] of the territory of the State’. It further explained
that even if other maritime boundaries could also be categorized as ‘true boundaries’, they
might not fall within the boundary exclusion of VCLT article 62(2)(a).
This discussion was
inconclusive but suggests that territorial sea boundaries may be exempt from termination on
the basis of fundamental changes, while other maritime boundaries (exclusive economic zone,
continental shelf and single purpose boundaries) are not. At any rate, States can prevent
termination of bilateral maritime boundaries on these grounds by taking foreseeable changes
to coastal geography into account in the delimitation process and explicitly referring to those
changes in their agreements.
Finally, the pacta tertiis principle provides that treaties cannot create obligations or rights for
third States without their consent.
This is consonant to Guiding Principle 9 for unilateral
Bilateral maritime boundaries can be ‘perfectly valid and binding on the treaty
level’ but contrary to international law ‘when the relations between the parties and a third State
are taken into consideration’.
Consequently, ‘[i]t is … not uncommon in maritime boundary
agreements for the parties to agree that they will negotiate with third parties in the future on
potentially overlapping jurisdiction’.
Moreover, maritime boundaries can be contested by
third States when their rights are infringed,
regardless of whether the constituting
arrangement anticipates such action.
UNCLOS article 311(3) affirms that, although States may generally derogate from UNCLOS
provisions in bilateral agreements, such agreements may not violate basic principles of
UNCLOS or affect rights attributed to third States. In fact, boundary agreements that violate
See paragraph 2(a).
Aegean Sea Continental Shelf (Greece v Turkey) (Jurisdiction)  ICJ Rep 3, para 85.
ILC, ‘Report of the Commission to the General Assembly on the work of the thirty-fourth session’ (3 May-
23 July 1982) UN Doc A/CN.4/SER.A/1982/Add.l (Part 2) 60-61. See also Thomas Giegerich (n 127) 1093.
UN Doc A/CN.4/SER.A/1982/Add.l (Part 2) (n 131) 61.
VCLT article 34.
See UN Doc A/CN.4/SER.A/2006/Add.1 (Part 2) (n 87) para 176.
Burkina Faso/Republic of Mali (n 109) para 47.
Cissé Yacouba and Donald McRae, ‘The Legal Regime of Maritime Boundary Agreements’, in David A
Colson and Robert W Smith (eds) International Maritime Boundaries, vol V (Martinus Nijhoff 2005) 3281,
See more about potential effects for third States in Julia Lisztwan (n 96) 176-177.
the land dominates the sea principle, or the rights of third States, might be seen as nullities.
At any rate, treaties cannot create obligations for States without their consent
of the ICJ have ‘no binding force except between the parties and in respect of that particular
This means that the stability of bilateral maritime boundaries, whether established
through agreements or judicial decisions, may be threatened if changes to relevant coastal
geography lead to a violation of the land dominates the sea principle or creation of new rights
for third States.
This article has explored the effects that coastal changes have on maritime entitlements, and
explained what States can do to minimize fluctuations of limits de lege lata through unilateral
claims, acquiescence and bilateral arrangements. Changing coastal geography is bound to have
an impact on maritime entitlements under UNCLOS because of the inherent link with land
territory, specifically the coastal front. Yet, the limits and boundaries demarcating the extent
of maritime entitlements can be stabilised in some instances, justifying a departure from a strict
reading of UNCLOS provisions governing maritime limits.
Normal baselines fluctuate in accordance with changing coastlines because they correlate to
the actual low-water line along coastlines and so too must the derived outer limits. Straight
baselines also change to reflect receding coastlines because they must continuously meet
relevant requirements of UNCLOS. Therefore, unilateral baselines and derived limits generally
cannot be stabilised except through artificial conservation of the coastline. However, straight
baselines at highly unstable deltaic coastlines maintain provisional stability when the low-
water line recedes and the outer limits of the continental shelf beyond 200 nm can be
permanently described in accordance with UNCLOS article 76(8) and (9). To acquire this level
of stability States must establish straight baselines in accordance with UNCLOS article 7(2)
and follow the procedural requirements of UNCLOS articles 76(8) and (9). It is noteworthy
that the stability afforded to straight baselines under article 7(2) is only available to coastlines
that are highly unstable due to the presence of a delta and other natural conditions and that
States must eventually adjust these baselines so that they conform to UNCLOS.
All baselines (excluding normal baselines) and outer maritime limits must be given due
publicity in accordance with UNCLOS articles 16, 47(9), 75, 76(9) and 84 and this includes
submitting relevant data to the UNSG. This is a necessary step for establishing the permanence
of continental shelf limits beyond 200 nm. Furthermore, this is an important step for making
unilateral maritime limits opposable to other States, particularly if the maritime limits are
excessive or if they become inconsistent with UNCLOS due to changes in relevant coastal
geography. Such limits can become opposable to other States on the basis of acquiescence if
no protests are raised following due publication. Therefore, unilateral limits can be stabilised
on the basis of tacit acceptance from other States but changing coastal geography will give rise
to new challenges and it may be very difficult to prove tacit acceptance of normal baselines
because these are not given due publicity with the UNSG. As with bilateral boundaries, this
stability is dependent on a form of consent.
See Geoffrey Marston (n 34) 156.
VCLT article 34.
Article 59 of the ICJ Statute.
What sets bilateral boundaries apart from unilateral limits is the obligation to delimit
boundaries through an agreement or other peaceful means. This means that an arrangement is
created that essentially relies on the consent of sovereign States, which carries with it binding
force. Bilateral boundaries possess a level of stability unattainable for unilateral limits and they
generally remain inviolable as coastlines change. However, two exceptions can threaten the
stability of bilateral maritime boundaries. First, certain maritime boundaries may be subject to
termination by reference to a fundamental change of circumstances, but only if the changes are
not anticipated in the delimitation process. Therefore, States would be well advised to consider
sea level rise and coastal erosion when delimiting bilateral maritime boundaries and provide
for such changes by express or implied terms. Second, circumstances may change and give rise
to new claims from third States to areas subject to previously settled maritime boundaries. Such
boundaries would not be opposable to third States under the pacta tertiis principle.
These conclusions demonstrate that there are ways to strengthen maritime claims as coastlines
retreat, which do not involve costly shoreline defences. The effects of coastal changes differ
depending on the legal basis for each claim and are, in the case of acquiescence, dependent on
a form of permission from the international community. In fact, widespread acquiescence to
threatened maritime limits might eradicate the need for legal reform or revised interpretation
of UNCLOS. This does not entail a general solution but the flexibility to afford stability to
instances or regions where severe loss of entitlements is imminent. Furthermore, this option
has the benefit of being available now, de lege lata.