The Law of Treaties

AuthorJohn H. Currie
Chapter 4
a. Nature aNd importaNCe of treaties
As described above,1 treaties are express and usua lly formalized agree-
ments between states or other subjects of intern ational law — they set
out the parties’ mutual legal rights and obligations, and are governed
by international law. They may take the form of reciprocal undertak-
ings between as few as two state s (“bilateral” tre aties), or more gen-
eralized agreements adhered to by several or even, on occasion, most
states in the world (“multilateral” treaties). Their subject matter ranges
from very specif‌ic undertaking-and-performance ag reements between
states — akin to domestic law contracts and therefore sometimes called
“treaty-contracts” — to broad codif‌ications or restatements of certain
substantive area s of intern ational law, designed to govern the ongoing
conduct of all the parties to them in the relevant subject-area (some-
times called “law-making” or “codif‌ication” treaties).
Treaties are thus supple legal tools in the hands of states, permit-
ting them to enter into individual relationships with other states on
very specif‌ic issues or projects, or to establish widely applicable norms
intended to govern legal relationships with as many other states as will
expressly agree to their terms. Indeed, in the twentieth and twenty-f‌irst
centuries states h ave even made use of treaties to reshape and redef‌ine
the structure of t he intern ational legal system itself. For exa mple, the
1 See Chapter 3, Sect ion C(2).
United Nations (UN), with its enormous institutional apparatus (in-
cluding the International Court of Justice), is merely the product of
one of the most succes sful and w idely rat if‌ied multilateral treaties of
all time, the Charter of the United Nations and its annexed Statute of the
Thanks largely to such institutional innovations, treatie s have had
pride of place in developing and clarifying international law in the past
century. Previously, customar y international law was clearly the pri-
mary source of generally applicable international norms, early treaty
practice being largely bilateral and situation-specif‌ic in nature. This
began to change in the late nineteenth and early twentieth centuries
with the elaboration of broader-based treaty regimes, mostly concerned
with the conduct of war and humanitarian law.3 The last ha lf of the
twentieth century, however, witnessed explosive growth in the number
of multilateral codif‌ication or law-making treaties in v irtually a ll areas
of the law.
As suggested above, this phenomenal growth can be attributed
partly to the establishment of international institutions such as the
United Nations and its agencies, wh ich have provided permanent fora
for the negotiation of such broad-based agreements.4 Of par ticular im-
portance to this process has been the work of the Internat ional Law
Commission (ILC), a panel of exper ts established by t he General As-
sembly of the United Nations in 1947 in partial fulf‌ilment of its mandate
to “encourage the progressive development of international law and its
codif‌ication.5 The ILC ha s been at the forefront of the “codif‌ication”
movement, steadily producing draft texts in a variety of f‌ields, texts
that have served as the starting point for state negotiations leading to
the conclusion of some of the most successful multilateral treaties.6
The rise in the relative import ance of treaties as a source of gener-
ally applicable international law can also in part be attributed to the
2 Charter of the United Nat ions, 26 June 1945, Can. T.S. 1945 No. 7 (entered into
force 24 October 1945) [UN Charter]; Statute of the Interna tional Court of Justice,
26 June 1945, Can. T.S. 1945 No. 7 (entered into force 24 October 1945) [ICJ
3 For example, Convention for th e Pacif‌ic Settlement of Interna tional Disputes
(Hague I), 29 July 1899, reproduced in J.B. Scott, The Hague Peace Conferen ces of
1899 and 1907, vol. II (New York: Garland, 1972) at 80; and Convention Respe ct-
ing the Laws and Customs of War on Lan d (Hague IV), 18 October 1907, repro-
duced in ibid. at 368.
4 See O. Schachter, “United Nat ions Law” (1994) 88 A.J.I.L. 1 at 1–2.
5 UN Charter, above note 2, Art icle 13(1). See also Chapter 3, Section D(2).
6 For a more thorough overview of the mandate, procedure, and work of the ILC,
see the Intern ational Law Commis sion’s homepage, online: w/ilc/.
The Law of Treaties 125
peculiar advantages offered by treaties as law-making dev ices. These
include the speed and clarity with which the law may be codif‌ied, cre-
ated, or adva nced, which has been importa nt in accommodating the
dramatically increased intensity and breadth of international discourse
since the Second World War.
Given their requirement of express consent, moreover, treaties
dovetail neatly with positiv ist notions of the source of binding obliga-
tion in international law. They represent t he ultim ate embodiment of
the t heory of consent and thus of the sovereignty of st ates.7 As such,
states may feel they are “tak ing cha rge” of their own legal obligations
by participat ing in multilateral t reaty negotiations, thus prov iding yet
more momentum to the multilateral treaty juggernaut.
Numerous terms have been coined to refer to treaties in one form or
another, the most common of which include “conventions,” “charters,”
“covenants,” “protocols,” “pacts,” “acts,” “statutes,” or, simply, “agree-
ments.” While various factors will inf‌luence states in their choice of
title for any particular treaty, the term used has no legal signif‌icance in
itself. All treaties, whatever their design ation, and as long as they rep-
resent the express will of the part ies to be bound by their terms in ac-
cordance with intern ational law, are equally binding upon the par ties.
b. the
It is one of the ironies of international law that the legal rules governing
the formation, legal effects, and dissolution of treaties have for the most
part evolved as a matter of customary international law.8 Through the
centuries states have, by their conduct and att itude, conf‌irmed th at an
express agreement between them must be honoured in good faith. They
7 See Chapter 3. Even th is most positivist of form al international lega l sources
has a natur al law seam runni ng through it, however. Although states ar e only
bound by treat ies to which they expressl y consent, once that consent is un -
conditionall y given it cannot unilatera lly be withdrawn. The f undamental rule
that treat ies must be performed in good f aith (see Section G(1), below in this
chapter) is a clear derogat ion from the theory of consent: s ee above Chapter 3,
Section C(2).
8 The role of domestic law is of cou rse also important i n the treaty formation
process, but th is chapter focuses on the inte rnational legal ru les governing
treaties. The s ignif‌icance of domestic cons titutional orders on treat y formation
and implementat ion will be discuss ed in Sections G(1) and I(2)(a), below in this
chapter, as well as i n Chapter 6.

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