Agreed maritime boundaries are final and binding, whether they are negotiated or judicially decided, as
they are subject to the general principle pacta sunt servanda.5 Treaties generally rely on the assumption that
certain circumstances, essential to the conclusion of the treaty, will remain unchanged. It is on the basis of
those circumstances that parties reach an agreement specifying their shared expectations and pacta sunt
servanda aims to safeguard these shared expectations.6 However, pacta sunt servanda does not provide that
all agreements remain inviolable till the end of time.7 When circumstances leading to the conclusion of a
treaty have changed and obligations under a treaty have become unduly burdensome, States can be freed
from their contractual obligations through peaceful means, by virtue of a different principle: rebus sic stan-
tibus.8 The doctrine of rebus sic stantibus allows for a treaty’s unilateral termination when an unforeseen
fundamental change of circumstance has affected the essential basis of the treaty. This customary rule is
codified in Article 62 of the Vienna Convention on the Law of Treaties (VCLT).9
VCLT Article 62(2)(a) explicitly excludes treaties establishing boundaries from its application. For that
reason, one might assume that maritime boundaries could never be set aside due to a fundamental change
of circumstances, such as the submergence of an island or the appearance of a new volcanic island. There
are however, no indicators that the original customary rule excluded maritime boundary treaties. Further,
when members of the International Law Commission (ILC) decided to exclude treaties establishing bounda-
ries from the application of VCLT Article 62, they never discussed the possibility of also excluding maritime
boundaries. The nature of maritime zones is different from that of land territory and the reason for exclud-
ing treaties establishing land boundaries, the need for stability, is not a necessary requirement of maritime
frontiers, which generally fluctuate with changes to the coastal front.10
This article provides a doctrinal analysis of VCLT Article 62, with particular emphasis on the ‘boundary’
concept. The origin and travaux préparatoires of the provision are examined, as well as the provision’s appli-
cation in relation to treaties establishing maritime boundaries. This analysis indicates that particular types
of maritime boundaries may indeed be set aside by virtue of VCLT Article 62 when relevant coastal geog-
raphy has undergone drastic and unforeseen changes, leading to the radical transformation of maritime
entitlements under UNCLOS. The exclusion of treaties establishing boundaries only applies to boundaries
delimiting sovereign territory and, consequently, does not cover boundaries delimiting the exclusive eco-
nomic zone, exclusive fisheries zone, or the continental shelf.
Rebus Sic Stantibus
: The Origin of VCLT Article 62
Gentilis, who wrote the first textbook in international law,11 introduced the maxim omnis conventio intel-
ligitur rebus sic stantibus12 in the sixteenth century. He is believed to have been the first legal scholar to
discuss the theory more generally known as rebus sic stantibus. Gentilis based his findings on the writings
of civil lawyers but according to Pal of the ILC, the theory derived from canon law.13 Its existence was later
affirmed by Suárez and Vattel but rejected by Grotius in the seventeenth century because he made a distinc-
tion between treaties and contracts and was reluctant to accept the termination of treaties due to changed
circumstances because of derivative complications.14 Bynkershoek is also said to have rejected the theory of
rebus sic stantibus in the eighteenth century, although he held that an impossibility of performance might
allow for derogation from treaty obligations.15 Such a contention does not necessarily reject the doctrine
of rebus sic stantibus since some members of the ILC did not distinguish between rebus sic stantibus and
impossibility of performance while drafting the articles for the VCLT.16 Several members wanted to merge
Frontier Dispute (Burkina Faso v Repblic of Mali) (Judgment) (1986) ICJ Rep 554, 577, para 46.
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.
Rein Müllerson, ‘The ABM Treaty: Changed Circumstances, Extraordinary Events, Supreme Interests and International Law’ (2001)
50 The International and Comparative Law Quarterly 509, 525.
Stein and Carreau (n 6) 617.
Vienna Convention on the Law of Treaties (adopted 23 May 1969, entered into force 27 January 1980) 1155 UNTS 331 (VCLT).
10 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.
11 Boleslaw A Boczek, International Law: A Dictionary (Scarecrow Press 2005) 9.
12 Every agreement is understood based on the existing circumstances.
13 ILC Summary Record ‘694th Meeting’ (6 June 1963) UN Doc A/CN.4/SR.694, 136.
14 See Hugo Grotius, De Jure Belli ac Pacis (trans Francis W Kelsey) in James B Scott (ed), The Classics of Internationial Law (vol 2, OUP
15 UN Doc A/CN.4/SR.694 (n 13) 136.
16 ibid 141.