It is beyond serious argument that states are required by international law to regulate and control activities within their territory or subject to their jurisdiction or control that pose a signifi cant risk of global or transboundary pollution or environmental harm.210 Th is is an obligation to take appropriate measures to prevent or minimize as far as possible the risk of signifi cant harm, not merely a basis for reparation aft er the event.211 It follows that states must also take measures to identify such risks, for example by environmental impact assessment or monitoring.212 Th e obligation is a continuing one: ‘It implies the need for States to review their obligations of prevention in a continuous manner to keep abreast with the advances in scientifi c knowledge.’213 Although some writers and treaties use the term ‘preventive principle’,214 the obligation referred to here is more than a principle—in regard to transboundary environmental risks it is an obligatory rule of customary international law. It has been identifi ed as such in arbitral and judicial decisions, in a wide range of global and regional treaties, and in the Stockholm and Rio Declarations.
(a) Customary law and Principle 2 of the Rio Declaration
In the Nuclear Weapons Advisory Opinion the ICJ held, as we saw earlier, that the terms of Principle 2 of the Rio Declaration are ‘now part of the corpus of international law relating to the environment’.215 Th e origins of a rule on transboundary harm can be traced to the well-known Trail Smelter Arbitration,216 in which a tribunal awarded
209 But see Articles 9 and 10, and the discussion of equitable balancing, infra, section 4(5).
210 On the meaning of ‘jurisdiction or control’ see ILC Report (2001) GAOR A/56/10, 383–5. It includes ships, aircraft , spacecraft , and occupied territory.
211 Article 3, ILC 2001 Articles on Transboundary Harm. See generally Handl in Bodansky, Brunnée, and Hey, Oxford Handbook of IEL, 532. On the origins of this rule see Dupuy in OECD, Legal Aspects of Transfrontier Pollution (Paris, 1977) 345; Smith, State Responsibility and the Marine Environment (Oxford, 1988) 36ff , 72ff ; Handl, 26 NRJ (1986) 405, 427ff ; Kirgis, 66 AJIL (1972) 290, 315; Quentin-Baxter, II YbILC (1980) Pt 1, 246–62; Lefeber, Transboundary Environmental Interference and the Origin of State Liability, Ch 2.
212 ILC Report (2001) GAOR A/56/10, 391, para (5). On EIA see infra, next section.
213 ILC Report (2001) GAOR A/56/10, 415, para (7). See Gabčíkovo-Nagymaros Case, ICJ Reports (1997) 7, para 140.
214 See e.g. de Sadeleer, Environmental Principles, Ch 2, and 1999 Rhine Convention, Article 4. Th e ‘pre-ventive principle’ is derived from EC law where it is not limited to global or transboundary harm.
215 ICJ Reports (1996) 226, para 29. See also Iron Rhine Arbitration, PCA (2005) paras 222–3.
216 33 AJIL (1939) 182 and 35 AJIL (1941) 684. See Read, 1 CYIL (1963) 213; Rubin, 50 Oregon LR (1971) 259; Kirgis, 66 AJIL (1972); Smith, State Responsibility, 72ff ; Quentin-Baxter, II YbILC (1981) Pt 1, 108ff .
damages to the United States and prescribed a regime for controlling future emis-sions from a Canadian smelter which had caused air pollution damage. It concluded that ‘no state has the right to use or permit the use of its territory in such a manner as to cause injury by fumes in or to the territory of another or the properties or per-sons therein, when the case is of serious consequence and the injury is established by clear and convincing evidence’, and prescribed control measures to avert future trans-boundary pollution.217 Th e judgment of the ICJ in the Corfu Channel Case supports a similar conclusion, although the context is rather diff erent and its application to the environment more doubtful. Here the court held Albania responsible for damage to British warships caused by a failure to warn them of mines in territorial waters, and it indicated that it was ‘every state’s obligation not to allow knowingly its territory to be used for acts contrary to the rights of other states’.218 Th is judgment does not sug-gest what the environmental rights of other states might be, and its true signifi cance may be confi ned to a narrower point about warning other states of known dangers, considered below.
While the signifi cance of these older judicial or arbitral precedents should not be overrated, there is ample evidence of continued international support for the broad proposition that states must control sources of harm to others or to the global environ-ment arising within their territory or subject to their jurisdiction and control.219 In par-ticular, Principle 21 of the 1972 Stockholm Declaration on the Human Environment is important, because it affi rms both the sovereign right of states to exploit their own resources ‘pursuant to their own environmental policies’ and their responsibility ‘to ensure that activities within their jurisdiction or control do not cause damage to the environment of other states or to areas beyond the limits of national jurisdiction’.
Although, as Professor Sohn has observed, the fi rst part of this principle comes ‘quite close’ to asserting that a state has unlimited sovereignty over its environment, the totality of the provision, including its emphatic reference to responsibility for envir-onmental damage, was regarded by many states present at the Stockholm Conference,
217 35 AJIL (1941) 716. Th is fi nding relied on the Alabama Claims Arbitration (1872) Moore, 1 International Arbitrations, 485, and Eagleton, Responsibility of States in International Law (1928) 80, for the general prop-osition that ‘A state owes at all times a duty to protect other states against injurious acts by individuals from within its jurisdiction’, and on the evidence of US Federal case law dealing with interstate air and water pollution, which it held ‘may legitimately be taken as a guide in this fi eld of international law . . . where no contrary rule prevails’, 35 AJIL (1941) 714. Reliance on domestic case law by analogy was not required by the compromis, which called for application of US law and practice only in respect of issues of proof of damage, indemnity, and the regime of future operations of the smelter, ibid, 698. Th e use of domestic law analogies is better treated as an invocation of ‘general principles of law’ referred to in Article 38(1) of the Statute of the ICJ. For criticism of the tribunal’s approach, see Rubin, 50 Oregon LR (1971) 267; Goldie, 14 ICLQ (1965) 1229, and for explanation, see Read, 1 CYIL (1963) 213.
218 ICJ Reports (1949) 22. See also Nuclear Tests Case (Australia v France) ICJ Reports (1974) 388, per de Castro; Lac Lanoux Arbitration, 24 ILR (1957) 101, 123; and Brownlie, State Responsibility (Oxford, 1983) 182.
219 See e.g. 1979 Convention on Long-range Transboundary Air Pollution; 1982 UNCLOS, Articles 192–
212; 1989 Convention on the Control of Transboundary Movements of Hazardous Wastes; 1991 Convention on EIA, Article 2; 1985 Convention for the Protection of the Ozone Layer; 1992 Framework Convention on Climate Change.
and subsequently by the UN General Assembly, as refl ecting customary international law.220
Moreover, whereas older formulations of the preventive obligation, in cases such as Trail Smelter, had dealt only with transboundary harm to other states, Stockholm Principle 21 and later conventions point to international acceptance of the proposition that states are also required to protect global common areas, including Antarctica and those areas beyond the limits of national jurisdiction, such as the high seas, deep sea-bed, and outer space.221 Article 194(2) of the 1982 UNCLOS makes the same point in relation to the prevention of pollution spreading beyond areas where a state exer-cises sovereign rights. At the 1972 Stockholm Conference, the United States stated that Principle 21 did not in any way diminish existing international responsibility for dam-age to areas beyond national jurisdiction; in its view it ‘affi rmed existing rules’.222 Th e UN General Assembly also resolved that in the exploration, exploitation, and devel-opment of their natural resources, ‘states must not produce signifi cant harmful eff ects in zones situated outside their national jurisdiction’.223 An important consequence of this changed perspective is that the obligation to prevent, reduce and control environ-mental harm is no longer solely bilateral in character but in relation to the high seas or the global atmosphere it benefi ts the international community as a whole and to that extent operates erga omnes.224
Th e Rio instruments confi rm the status of Stockholm Principle 21 as a statement of contemporary international law. It is repeated verbatim in Article 3 of the Convention on Biological Diversity, reiterated with one minor change in Principle 2 of the Rio Declaration, and extended to the global atmosphere by the preamble to the Convention on Climate Change.225 In its revised form Principle 2 now provides that:
States have, in accordance with the Charter of the United Nations and the principles of international law, the sovereign right to exploit their own resources pursuant to their own
220 Sohn, 14 Harv ILJ (1973) 491ff . Several states declared that Principle 21 accorded with existing inter-national law: see Canadian and US Comments in UN Doc A/CONF 48/14/Rev 1, 64–6. UNGA Res 2996 (XXVII) (1972) asserts that Principles 21 and 22 of the Stockholm Declaration ‘lay down the basic rules governing the matter’. See also UNGA Res 2995 XXVII (1972); 2996 XXVII (1972); 3281 XXIX (1974); 34/186 (1979); UNEP Principles of Conduct in the Field of the Environment Concerning Resources Shared by Two or More States, Principle 3, UNEP/IG/12/2 (1978).
221 1967 Outer Space Treaty; 1979 Moon Treaty; 1972 London Dumping Convention; 1982 UNCLOS, Articles 145, 209; 1991 Protocol to the Antarctic Treaty on Environmental Protection. See Sohn, 14 Harv ILJ (1973) 423; Smith, State Responsibility and the Marine Environment (Oxford, 1988) 76ff ; Fleischer, in Bothe, Trends in Environmental Policy and Law, 321; Charney, in Francioni and Scovazzi (eds), International Responsibility for Environmental Harm (Dordrecht, 1991) 149; Pineschi, in Francioni and Scovazzi (eds), International Law for Antarctica (2nd edn, Th e Hague, 1996) 261.
222 Report of the UN Conference on the Human Environment, UN Doc A/CONF/48/14/Rev 1, (1972) para 327.
223 UNGA Res 2995 XXVII (1972).
224 Charney, in Francioni and Scovazzi, International Responsibility for Environmental Harm, and see supra section 3(2) on erga omnes obligations.
225 See also preambles to 1994 Convention to Combat Desertifi cation; 2001 Convention on Persistent Organic Pollutants; 2006 International Tropical Timber Agreement; 2008 Non-Legally Binding Instrument on all Types of Forests, UNGA Res 62/98.
environmental and developmental policies, and the responsibility to ensure that activities within their jurisdiction or control do not cause damage to the environment of other states or of areas beyond the limits of national jurisdiction.
Although the reference to a state’s own developmental policies constitutes an add-itional qualifi cation of its environmental responsibilities, it is doubtful whether this does more than confi rm an existing and necessary reconciliation with the principle of sustainable development and the sovereignty of states over their own natural resources.
It is an exaggeration to see this textual change as eviscerating or signifi cantly amend-ing the existamend-ing responsibility of states in international law for the control and preven-tion of environmental harm.226 As Sands observes:
a careful reading suggests that the additional words merely affi rm that states are entitled to pursue their own developmental policies. Th e introduction of these words may even expand the scope of the responsibility not to cause environmental damage to apply to national devel-opmental policies as well as national environmental policies.227
As we noted earlier, Principle 2 is neither an absolute prohibition on environmental damage, nor does it confer on states absolute freedom to exploit natural resources.
Like sustainable development, it requires integration or accommodation of both eco-nomic development and environmental protection.228 Th is feature of Principle 2 must be taken into account when interpreting both parts of the rule which it articulates. In practice, the relationship between the sovereign use of resources and the responsibil-ity for environmental protection has usually been negotiated in the context of specifi c sectoral treaty regimes, and it may diff er in diff erent contexts. Treaties dealing with climate change or land-based sources of marine pollution thus allow rather more lati-tude for resource use which causes environmental damage than do those concerned with pollution from ships or nuclear accidents.229 In its work on international water-courses the ILC found it a challenge to determine the right balance between the free-dom to make equitable use of an international watercourse and the duty not to cause harm to other riparian states.230 Both the need for balance and its context-specifi c nature in individual situations make it more diffi cult, but certainly not impossible, to apply Principle 2 in legal disputes between states. Despite its age, the Trail Smelter Arbitration illustrates very well how even a judicial or arbitral tribunal can fi nd ways of reconciling the prevention of transboundary harm with economic development.
In the following sections we consider how this can be achieved, and how Principle 2 should be interpreted.
226 Contra, Pallemaerts, in Sands, Greening International Law, 5–7.
227 Sands, Principles of International Environmental Law, 54–5. 228 Supra section 2(1).
229 See infra, Ch 6, 7, 8, 9.
230 Compare Articles 5 and 7 of the 1997 UN Watercourses Convention with the same articles in the ILC’s 1994 Draft Convention, UN Doc A/CN 4/L492 and Add 1 and compare the ILA’s 1966 Helsinki Rules, Article 10(1) and see infra, Ch 10.
(b) Th e normative contours of Principle 2
Whatever the signifi cance of Trail Smelter and older judicial precedents may have been, the main importance of Principle 2 is that it recognizes the need to take measures to prevent or minimize harm to the environment of other states or the global commons.
Even in Trail Smelter, Canada was ordered by the tribunal to take measures to prevent or reduce future injury, and this is the primary purpose of most modern environmen-tal treaties, including the Ozone Convention, the MARPOL Convention, the London Dumping Convention, the POPS Convention and others dealing with land-based pol-lution, desertifi cation, or climate change. Th at the rule is now primarily one of regula-tion and control is indicated most clearly by its formularegula-tion in Article 194 of the 1982 UNCLOS:
States shall take, individually or jointly as appropriate, all measures consistent with (1)
this Convention that are necessary to prevent, reduce and control pollution of the marine environment from any source, using for this purpose the best practicable means at their disposal and in accordance with their capabilities, and they shall endeavour to harmonise their policies in this connection.
States shall take all measures necessary to ensure that activities under their jurisdiction (2)
or control are so conducted as not to cause damage by pollution to other states and their environment . . .231
Th e same approach is found in Article 2(1) of the 1991 Convention on Transboundary Environmental Impact Assessment, and in Article 3 of the 2001 Articles on Prevention of Transboundary Harm. Th e former provides that: ‘Th e parties shall, either indi-vidually or jointly, take all appropriate and eff ective measures to prevent, reduce and control signifi cant adverse transboundary environmental impact from proposed activities.’ Th e latter requires parties to take ‘all appropriate measures to prevent or minimise the risk of signifi cant transboundary harm’. What these formulations imply is an obligation to act with due diligence.232
In general terms, ‘due diligence’ addresses two issues. First, it requires the introduc-tion of policies, legislaintroduc-tion, and administrative controls applicable to public and pri-vate conduct which are capable of preventing or minimizing the risk of transboundary harm to other states or the global environment, and it can be expressed as the conduct to be expected of a good government.233 Following the Sandoz disaster, Switzerland thus accepted that it had failed to regulate spills from pharmaceutical plants to the standard required by the 1976 Rhine Chemicals Convention.234 Th is is not an obliga-tion of result: ‘Th e duty of due diligence . . . is not intended to guarantee that signifi cant
231 See infra, Chs 7, 8.
232 ILC Report (2000) GAOR A/55/10, para 718: ‘the special rapporteur was of the opinion that “all appro-priate measures” and “due diligence” were synonymous’.
233 ILC 2001 Articles, Article 3 and commentary, ILC Report (2001) GAOR A/56/10, 393–5, paras (10)–
(17); OECD, Legal Aspects of Transfrontier Pollution, 385f; Dupuy, ibid, 369ff ; Smith, State Responsibility and the Marine Environment, 36–42; Pisillo-Mazeschi, 35 GYIL (1992) 9.
234 ILC Report (2001) GAOR A/56/10, 392. See Kiss, 33 AFDI (1987) 719–27.
harm be totally prevented, if it is not possible to do so.’235 To that extent it remains lawful to conduct inherently harmful or risky activities such as nuclear power plants.
Moreover, states are responsible only for their own failure to act diligently, not for any failure by the operator to do so.236 In the Pulp Mills Case, much of the argument thus focused on the adequacy of Uruguay’s regulatory system, its provision for EIA, and the choice of technology. Considerations of the eff ectiveness of territorial control, the resources available to the state, the degree of risk, and the nature of specifi c activities may also be taken into account and justify diff ering degrees of diligence.237 Th e ILC commentary has summarized the key points:
Th e standard of due diligence against which the conduct of State of origin should be exam-ined is that which is generally considered to be appropriate and proportional to the degree of risk of transboundary harm in the particular instance. For example, activities which may be considered ultra-hazardous require a much higher standard of care in designing policies and a much higher degree of vigour on the part of the State to enforce them. Issues such as the size of the operation; its location, special climate conditions, materials used in the activ-ity, and whether the conclusions drawn from the application of these factors in a specifi c case are reasonable, are among the factors to be considered in determining the due diligence requirement in each instance. What would be considered a reasonable standard of care or due diligence may change with time; what might be considered an appropriate and reason-able procedure, standard or rule at one point in time may not be considered as such at some point in the future. Hence, due diligence in ensuring safety requires a State to keep abreast of technological changes and scientifi c developments.238
Secondly, due diligence entails an evolving standard of technology and regulation.
Th is is commonly expressed by reference to the use of ‘best available techniques’, ‘best practicable means’, or ‘best environmental practices’.239 Comparison with standards followed by other states will oft en be a good guide in this context. Th is approach allows for the standard of diligence to change as technology and operating techniques develop and for new industrial plants to operate to higher standards than existing
235 ILC Report (2001) GAOR A/56/10, 391–2, para (7), and to the same eff ect but in a rather diff erent context, Bosnian Genocide Case, ICJ Reports (2007) para 430: ‘A State does not incur responsibility simply because the desired result is not achieved; responsibility is however incurred if the State manifestly failed to take all measures to prevent genocide which were within its power and which might have contributed to preventing the genocide.’ See generally Handl in Bodansky, Brunnée, and Hey, Oxford Handbook of IEL, 538–40, and Dupuy, 10 EJIL (1999) 371–85.
236 ILC Report (2001) GAOR A/56/10, 399, para (3); OECD, Legal Aspects of Transfrontier Pollution, 380;
Dupuy, ibid. See, for a good example, 1982 UNCLOS, Annex III, Article 4(4).
237 See generally Alabama Claims Arbitration, supra n 217, 485; Corfu Channel Case, ICJ Reports (1949) 89, Judge ad hoc Ecer; Case Concerning Diplomatic and Consular Staff in Tehran, ICJ Reports (1980) 29–33;
Bosnian Genocide Case, ICJ Reports (2007) para 430; Dupuy, in OECD, Legal Aspects of Transfrontier Pollution, 375f; Smith, State Responsibility and the Marine Environment, 38–41.
238 ILC Report (2001) GAOR A/55/10, 394, para (11).
239 For a comprehensive defi nition of the terms ‘best available techniques’ and ‘best environmental prac-tices’ see Article 5(f) and Annex C of the 2001 POPS Convention. See also 1992 OSPAR Convention for the Protection of the Marine Environment of the Northeast Atlantic, Article 2(3) and BAT standards adopted by the OSPAR Commission, infra, Ch 8.
plants. Th us, in the Pulp Mills Case, Uruguay’s newly built mills would have to operate
plants. Th us, in the Pulp Mills Case, Uruguay’s newly built mills would have to operate