Treaties and custom have historically been the main sources of binding international law, augmented since the adoption of Article 38(1) of the Statute of the Permanent Court of International Justice in 1920 by general principles of law and, as secondary sources, judicial decisions and the teachings of the most highly qualifi ed publicists.66 Th ough draft ed before the growth in the number and diversity of states or the emergence of environmental consciousness, Article 38(1) remains the only generally accepted state-ment of the sources of international law to be applied by the ICJ. It is open to question whether it represents an exhaustive listing. Other possible candidates include General Assembly Resolutions, Declarations of Principles adopted by the UN or by ad hoc con-ferences, treaty provisions agreed by general consensus among the majority of states but not yet in force, and the proposals of the International Law Commission. Some commentators consider that norms drawn from these sources have to be embodied in treaties or state practice before they can become binding on states. Others are content to regard such sources as good evidence of existing customary law, or at least of the opinio juris necessary to turn state practice into custom.67
(a) Treaties68
Treaties are now the most frequently used instruments for creating generally applic-able multilateral rules relating to the environment. Th e 1992 Conventions on Climate Change and Biological Diversity, or the 1982 UNCLOS, are, in this sense, lawmaking treaties.69 Th ey create regimes to which almost all states are party and from which no reservations or derogations are possible unless expressly authorized. Treaties of this kind are the most important basis for international environmental law.
Essentially, a treaty is a written or oral agreement between states, or between states and international organizations, governed by international law. Th e terminology is immaterial: the variety of alternatives includes treaty, convention, protocol, covenant,
64 See generally Fitzmaurice, 25 NYIL (1994) 181, and infra, section 2(6).
65 For succinct accounts of sources, a discussion of the term itself, and analysis of Article 38 of the ICJ Statute, see Brownlie, Principles of Public International Law (6th edn, Oxford, 2005) Ch 1, and Higgins, International Law and How we Use it (Oxford, 1994) Ch 2. See also Danilenko, in Butler (ed), Perestroika and International Law (Dordrecht, 1990) 61; Cassese, International Law in a Divided World (Oxford, 1986);
Macdonald and Johnston (eds), Th e Structure and Process of International Law (Dordrecht, 1983) and van Hoof, Rethinking the Sources of International Law (Deventer, 1983).
66 See now Statute of the International Court of Justice, Article 38(1).
67 See generally Boyle and Chinkin, Th e Making of International Law, Chs 4, 5.
68 See Brownlie, Principles of Public International Law, Ch 27; Aust, Modern Treaty Law and Practice (2nd edn, Cambridge, 2007); Sinclair, Th e Vienna Convention on Treaties (2nd edn, Manchester, 1984); Reuter, Introduction to the Law of Treaties (2nd edn, London, 1995).
69 On lawmaking treaties see Brölmann, 74 Nordic JIL (2005) 383.
pact, act, etc. Th ere are no rules prescribing their form but the 1969 Vienna Convention on the Law of Treaties codifi es rules applicable to written treaties concluded aft er its entry into force in 1980. Whilst not all provisions of this convention have necessarily attained the status of customary law, in practice it has been applied without question in many international and national judicial decisions.70 It deals with such matters as entry into force, reservations, interpretation, termination, and invalidity. Some agree-ments are executed in a simplifi ed form, by exchange of notes or letters, and become binding on signature without need for reference to parliaments. Others, concluded at the administrative level in the form of Memoranda of Understanding (MOU), are not necessarily binding but they may still be taken into account or create good faith expectations.71
A brief summary of the provisions of the Vienna Convention concerning the pro-cess of concluding a treaty will assist the uninitiated reader. Th e underlying principle of customary law is that pacta sunt servanda (treaties are made to be kept). Treaties are normally signed following their adoption, but unless there is specifi c agreement to be bound by signature, it is not until instruments of ratifi cation or accession have sub-sequently been deposited (which generally requires approval by national parliamen-tary or other internal processes) and any other requirements for entry into force have been fulfi lled (for example a specifi ed number of ratifi cations) that the treaty enters into force and becomes binding on its parties. Delays frequently occur at this stage.
Th is is not always the case, however—the rapid entry into force of the 1985 Vienna Convention for Protection of the Ozone Layer and its Montreal Protocol indicates that multilateral treaties can provide an effi cient means of urgent global or regional law-making when necessary.
Treaties do not ipso facto bind non-parties, unless the intention to do so is clearly expressed and the state concerned expressly accepts the benefi ts or obligations in ques-tion; in the latter case this must be done in writing. Th is is relatively unusual. Much more commonly treaty provisions bind non-parties through their evolution into cus-tomary international law, an argument considered in the next section. To be capable of so doing the ICJ has ruled in the North Sea Continental Shelf Case that ‘It would in the fi rst place be necessary that the provision concerned should, at all events potentially, be of a fundamentally norm-creating character such as could be regarded as forming the basis of a general rule of law’.72 As we shall see in Chapter 3, this fi rst requirement is one reason for doubting the status of sustainable development or the precautionary principle as ‘rules’ of customary international law. Th e second requirement laid down by the ICJ is that the provision in question should have been adopted in the practice of a suffi ciently widespread and representative number of states, including those that are not parties to the treaty. Moreover, the requirement of opinio juris, which establishes the legally binding character of state practice in customary law, must also be satisfi ed.
70 See in particular Gabčíkovo-Nagymaros Case, ICJ Reports (1997) 7.
71 Iron Rhine Arbitration, PCA (2005) paras 142, 157. See generally Aust, 35 ICLQ (1986) 787–812.
72 ICJ Reports (1969) 3, para 72.
Th ese two constitutive elements of custom—state practice and opinio juris—are con-sidered further below.
However, many environmental treaties do not necessarily contain clear, detailed, or specifi c rules. Sometimes they lay down only a framework of general principles or requirements for states ‘to take measures’ or ‘all practicable measures’, as in the case of the 1992 Framework Convention on Climate Change, the 1985 Convention for the Protection of the Ozone Layer or the 1979 Convention on Long-range Transboundary Air Pollution.73 Insofar as these require further action by states to prescribe the precise measures to be taken, they may necessitate the conclusion of more specifi c agreements, adding protocols or annexes to existing conventions, or adopting non-binding guidelines or recommendations. Another example of this ‘framework treaty’
approach is the 1979 Bonn Convention on Conservation of Migratory Species of Wild Animals whose implementation requires conclusion of agreements between ‘range states’ and the listing of species on its appendices for its eff ective operation.74 In eff ect such treaties become regulatory regimes through which an increasingly complex pat-tern of detailed rules and standards evolves.75 Regulatory treaties can also be con-cluded in the form of an ‘umbrella’ instrument consisting of a general convention linked to one or more treaties on specifi c issues. Th e 1982 UNCLOS is an example.
Although lacking any formal provision for the adoption of further protocols or annexes, it makes frequent reference to ‘generally accepted international rules and standards’,76 it envisages the adoption of regional agreements on various matters, and it must be read together with subsequently adopted ‘implementation agreements’, including the 1994 Agreement Relating to Part XI,77 and the 1995 UN Fish Stocks Agreement.78 Rather like protocols to a framework convention, these agreements interpret, amplify and develop the existing provisions of UNCLOS. Th ey also provide alternative models for what is in eff ect, although not in form, inter se amendment of the Convention.79 Unlike protocols to environmental framework treaties, however, implementing agreements can be free-standing treaties, independent of participa-tion in UNCLOS itself.
Framework or umbrella treaties can still infl uence the development of customary law insofar as they establish support for certain basic rules or principles, but this may not apply to the more detailed standards laid down in regulatory protocols or annexes,
73 See infra, Ch 6, and on the principle of due diligence, Ch 3, section 4. 74 See infra, Ch 12.
75 See e.g. the 1973/8 MARPOL Convention, infra,Ch 7, the 1985 Ozone Convention, and the 1979 Convention on Long-range Transboundary Air Pollution, infra, Ch 6.
76 See infra, Ch 7. 77 See Anderson, 43 ICLQ (1994) 886; Charney, 35 VJIL (1995) 381.
78 See FAO, Structure and Process of the 1993–1995 UN Conference on Straddling Fish Stocks and Highly Migratory Fish Stocks (Rome, 1995) and infra, Ch 13.
79 Th e use of an ‘implementing agreement’ was deliberately intended to avoid ‘amendment’ of the Convention. Nevertheless, the 1994 Agreement on Part XI disapplies certain provisions of Part XI and revises others. It also prevails over inconsistent provisions of the Convention. Non-parties are assumed to have acquiesced in the changes made to the Convention. Th is looks very like amendment in practice. Th e 1995 Fish Stocks Agreement neither specifi cally amends UNCLOS nor does it prevail over it, but it does make signifi cant changes in the applicable law.
which are in any case less likely to be followed in practice by non-parties. It is common, moreover, to separate such technical standards from the basic provisions of the treaty in order to allow for ease of amendment in the light of technical or scientifi c experi-ence. Th is is why they will usually be found in protocols or annexes, as in most marine pollution conventions, or in schedules, as in the 1946 International Convention for the Regulation of Whaling (ICRW).80 Th e provisions of protocols, annexes or sched-ules of this kind are not always binding on all the parties to a treaty; in many cases states are free to opt out by objecting within an appropriate time aft er adoption or s ubsequently.81 Th us it should not be assumed that every treaty provision has been transformed into customary law, even if widely followed, or that every part of a treaty is binding on all parties.
Th e 1969 Vienna Convention on the Law of Treaties liberalized treaty-making in a number of ways. In particular, it allowed states to participate à la carte—i.e. with reservations excluding provisions to which they objected, subject only to consistency with the treaty’s object and purpose.82 However, most global environmental treaties prohibit all reservations in order to preserve the integrity of what is usually a ‘package deal’ compromise text,83 or they permit only certain kinds of reservations.84 Th e possi-bility of making reservations normally encourages wider participation in treaties; it is partly their impermissibility under the 1982 UNCLOS that delayed this treaty achiev-ing the sixty ratifi cations required for entry into force and that has kept the US out of several environmental agreements. On the other hand, reservations also undermine the eff ectiveness of treaties by enabling states to protect their own economic and other interests. In practice, most multilateral environmental treaties are very widely rati-fi ed despite the ban on reservations. But most also allow any party to opt of detailed regulatory annexes, amendments, or additional protocols, either by withholding their consent or through ‘objection procedures’.85 Th is weakness is especially pertinent to adoption of stronger control measures or the listing of additional polluting substances or endangered species.86 Th ese details matter; participation only in an empty frame-work treaty amounts to little more than symbolic commitment to a process without the substance.
So far as interpretation of treaties is concerned, the Vienna Convention’s provi-sions87 include all three major schools of thought on the subject—the literal, the
80 See infra, Chs 7, 8, 12, 13. 81 See infra, Ch 2.
82 Articles 19–23. See Reservations to the Genocide Convention Case, ICJ Reports (1951) 15; Brownlie, Principles of Public International Law, Ch 27; Redgwell, 64 BYIL (1993) 245.
83 E.g. 1982 UNCLOS, Articles 309–10; 1985 Ozone Layer Convention, Article 18; 1989 Convention on Transboundary Movements of Hazardous Wastes, Article 26; 1992 Climate Change Convention, Article 24;
1992 Biological Diversity Convention, Article 37; 1994 Desertifi cation Convention, Article 37.
84 E.g. 1946 International Convention for the Regulation of Whaling. 85 Infra, Ch 2, section 5.
86 E.g. the 1997 Kyoto Protocol, infra, Ch 6; 1998 PIC Convention, infra, Ch 8; 1973 CITES, infra, Ch 12;
1946 Whaling Convention, infra, Ch 13.
87 Articles 31–3.
‘eff ective’, and the teleological approaches.88 Th us, the ordinary meaning of the words to be interpreted must fi rst be sought but in their broad context in the convention. Th e interpretation must be made in good faith and be compatible with the objects and pur-poses of the convention, which means that an interpretation must be adopted, so far as is possible, which makes the convention eff ective, a particularly valuable rule in the case of treaties with environmental objectives.89 Lastly, if the wording is ambiguous, recourse may be had to the travaux préparatoires (preparatory documents) to verify the interpretation derived from the above processes. Although the Convention for-mally applies only to treaties concluded by parties aft er its entry into force, its provi-sions on interpretation have been treated by all international courts as customary law, and on that basis they have been used to interpret earlier treaties or treaties between states not party to the Vienna Convention.90
Th e Vienna Convention’s articles on interpretation provide one of the most import-ant techniques for integrating diff erent treaties or bodies of law. Th e subsequent practice of the parties, or any agreement regarding interpretation of a treaty, must obviously be taken into account.91 Th e task of giving guidance on or amplifying the terms of envir-onmental treaties is performed most frequently by resolutions, recommendations, and decisions of other international organizations, and by the conferences of parties to treaties. Environmental soft law is quite oft en important for this reason, setting detailed rules or more general standards of best practice or due diligence to be achieved by the parties in implementing their obligations. Th ese ‘ecostandards’ are essential in giving hard content to the open-textured terms of framework environmental treaties.92 Th us UNEP’s Cairo Guidelines on the Transport of Hazardous Wastes93 can be regarded as an amplifi cation of the obligation of ‘environmentally sound management’ pro-vided for in Article 4 of the 1989 Basel Convention on the Control of Transboundary Movements of Hazardous Wastes. Th e advantages of regulating environmental risks in this way are that the detailed rules and standards can easily be changed or strength-ened as scientifi c understanding develops or as political priorities change. Th ey could of course be adopted in treaty form, using easily amended annexes to provide fl exibil-ity, but the parties may prefer a more cautious option.
Article 31(3)(c) of the Vienna Convention additionally provides that in interpret-ing a treaty, account shall also be taken of any other ‘relevant rules of international law applicable in the relations between the parties’.94 Doing so may help to avoid
88 Sinclair, Th e Vienna Convention on Treaties, 114–58.
89 See e.g. the Iron Rhine Arbitration, PCA (2005) paras 45–8, 85–91.
90 Territorial Dispute (Libyan Arab Jamahiriya/Chad), ICJ Reports (1994) 6, para 41; Kasikili/Sedudu Island (Botswana/Namibia), ICJ Reports (1999) 1045, para 18; Sovereignty over Pulau Ligitan and Pulau Sipadan (Indonesia/Malaysia), ICJ Reports (2002) 625, paras 37–8; Iron Rhine Arbitration (Belgium/
Netherlands), PCA (2005) para 45.
91 Article 31(3)(a)–(b).
92 See Contini and Sand, 66 AJIL (1972) 37; Bodansky, 98 Proc ASIL (2004) 275.
93 UNEP/WG 122/3 (1985), infra, Ch 8.
94 See McLachlan, 54 ICLQ (2005) 279; French, 55 ICLQ (2006) 281.
confl icts between agreed norms, or save negotiated agreements from premature obsolescence, or the need for constant amendment.95 Changes in international law and changing social values expressed in international policy can be taken into account and refl ected in the jurisprudence, a point particularly well observed in international human- rights law.96
How far, if at all, might re-interpretation of a lawmaking treaty be possible under this provision? Th e terms within which ‘evolutionary interpretation’ is permis-sible under Article 31(3)(c) have been narrowly circumscribed in the jurisprudence, and over-ambitious attempts to reinterpret or ‘cross-fertilize’ treaties by reference to later treaties or other rules of international law have had only limited success.97 Nevertheless, while accepting ‘the primary necessity of interpreting an instrument in accordance with the intentions of the parties at the time of its conclusion’, the ICJ has acknowledged that treaties are to be ‘interpreted and applied within the frame-work of the entire legal system prevailing at the time of the interpretation’.98 Th us, its approach in cases such as the Namibia Advisory Opinion and Aegean Sea is based on the view that the concepts and terms in question ‘were by defi nition evolutionary’,99 not on some broader conception applicable to all treaties. Th e WTO Appellate Body has given a similarly evolutionary interpretation to certain terms in the 1947 GATT Agreement. In the Shrimp-Turtle decision, for example, it referred inter alia to the 1992 Rio Declaration on Environment and Development, the 1982 UNCLOS, the 1973 CITES Convention, the 1979 Convention on Conservation of Migratory Species, and the 1992 Convention on Biological Diversity in order to determine the present mean-ing of ‘exhaustible natural resources’.100
In all of these cases the question at issue was not general revision or re- interpretation of the treaty. Rather, each case was concerned with the interpretation of particu-lar provisions or phrases, such as ‘natural resources’, or ‘jurisdiction’, which neces-sarily import—or at least suggest—a reference to current general international law.
Ambulatory incorporation of the existing law, whatever it may be, enables treaty pro-visions to change and develop as the general law itself changes, without the need for
95 For a particularly good example see the Iron Rhine Arbitration, PCA (2005) paras 58–9.
96 See infra, Ch 5.
97 Eg Ireland’s unsuccessful attempt to rewrite UNCLOS in the Mox Plant Arbitration (PCA, 2002). For a contrary view see Sands, in Boyle and Freestone (eds), International Law and Sustainable Development, 39.
98 Namibia Advisory Opinion, ICJ Reports (1971) 16, 31; Aegean Sea Continental Shelf Case, ICJ Reports (1978) 3, 32–3. Th e ICJ’s approach, combining both an evolutionary and an inter-temporal element, refl ects the ILC’s commentary to what became Article 31(3)(c). See ILC, ‘Th e law of treaties’, commentary to draft Article 27, para (16), in Watts (ed), Th e International Law Commission 1949–1998 (Oxford, 1999), vol II, 690.
99 See also Oil Platforms Case, ICJ Reports (2003) paras 40–1; La Bretagne Arbitration (Canada/France) (1986) 82 ILR 591, paras 37–51.
100 Import Prohibition of Certain Shrimp and Shrimp Products, WTO Appellate Body (1998) WT/DS58/
AB/R, paras 130–1.
any amendment. As the ICJ points out in the Oil Platforms Case, such treaty provi-sions are not intended to operate independently of general international law.101
Evolutionary interpretation is thus a relatively limited task, usually justifi ed by ref-erence to the intention of the parties and the object and purpose of the treaty. It does not entitle a court or tribunal to engage in a process of constant revision or updating every time a newer treaty is concluded that relates to similar matters.102 On this view, interpretation is interpretation, not amendment or rewriting of treaties. Th e result must remain faithful to the ordinary meaning and context of the treaty, ‘in the light of its object and purpose’.103
Whether another treaty is regarded as an agreement on interpretation, or as a guide
Whether another treaty is regarded as an agreement on interpretation, or as a guide