When will a state be liable and what is the requisite standard of proof?
In the case of Trail Smelter Arbitration,[5] it was found that the obligation arises if there is actual and serious harm which is likely to occur. Moreover, the Corfu Channel Case[6] suggested that the obligation also arises where there is a known risk to other states. 

It is crucial to then determine whether states are only liable in situations where a risk of actual harm is known to a state, or if state liability extends to situations where there is scientific uncertainty. Particularly, situations where there is lack of scientific certainty in matters of causation and prediction of long-term effects.[7] The question then becomes, whether in those situations, it can be said that international law adopts the precautionary principle (PP) or approach, which suggests that the states should take precautions even in the absence of clear evidence of harm and notwithstanding the costs of such action.[8]  

Scientific uncertainty
To provide some clarity to the readers, scientific uncertainty is generally understood to mean, that measures against an action cannot be justified on the basis that the risk of the action’s environmental harm is well-understood,[9] or that a prediction of its long-term effects is difficult to quantify. It covers a whole range of methodological, [10] epistemological and even ontological problems inherent in the practice of science.[11]

Defining the Precautionary Principle

States have long recognised that it is generally preferable to prevent pollution beforehand, rather than to deal with pollution after it has occurred.[12] Achieving that, necessitates the pursuance of certain preventive measures. At the core of this view, lies the notion of precautionary thinking, that action should be taken in advance of scientific certainty to protect the environment from incurring harm.[13] An early example demonstrating the effectiveness of successful precautionary action, being Dr John Snow’s decision in 1854.[14] Dr Snow recommended the removal of the handle of a water pump in London, in order to stop a cholera epidemic. At the time, the evidence supporting a causal link between cholera spread and polluted waters could not be described as proof beyond reasonable doubt, or as per the statement “clear and convincing scientific proof of actual or threatened harm.” Nevertheless, Dr Snow recommended the action, which ultimately stopped the cholera spread. The importance of such thinking is better understood bearing in mind that the cost, had Dr. Snow been wrong would only amount to some inconvenience or frustration suffered, whereas the cost of inaction would have been far greater, considering that the epidemic would continue.  

Several principles have developed under international environmental law, most of whom can be traced back to the 1930s.[15] Examples of such principles being sustainable development and the preventive principle. On the other hand, the precautionary principle only began to appear in international legal instruments in the mid-1980s,[16] while its origins are attributed to pre-1970 Swedish and German national environmental law.[17] After considering the various definitions, it can be observed that both strong and weak versions of the PP share some common elements. In particular, they both emphasise the anticipation of harm and the pursuance of precaution measures in light of scientific uncertainty. It can therefore be said that the precautionary principle is based on three core elements. Those being potential harm, scientific uncertainty and precautionary action.[18] The primary concern for decision makers under the PP being, to predict and avoid harm, where the harm to be avoided need not be a certain outcome of an action but it is sufficient that it is scientifically probable.[19] The maxims of “when in doubt, don’t”[20] and “primum non nocere”[21] being relevant.

After considering the various definitions, it can be observed that both strong and weak versions of the PP share some common elements. In particular, they emphasise the anticipation of harm and the pursuance of precaution measures in light of scientific uncertainty. It can therefore be said that the precautionary principle is based on three core elements. Those being (1) potential harm, (2) scientific uncertainty and (3) precautionary action.[22] The primary concern for decision makers under the PP being, to predict and avoid harm, where the harm to be avoided need not be a certain outcome of an action but it is sufficient that it is scientifically probable.[23] The maxims of “when in doubt, don’t”[24] and “primum non nocere”[25] being relevant.

The role of the Precautionary Principle

The rationale behind the application of the precautionary principle, appears to be that the consequences of scientific false positives, which are predominantly economic would by far outweigh the consequences of false negatives, which usually result in the loss of lives.[26] An example of the above rationale would be the argument, as put forward by Talbot Page in 1978, that a false negative, such as the allowing of a hazardous chemical would result in human lives being lost, while a false positive, for instance banning a harmless chemical would only have economic consequences.[27] In his view, “by definition, the potential costs of environmental risks are great and the benefits are generally modest.”[28] It therefore seems that the argument asserted above fits the notion of precautionary thinking as practiced by Dr Snow, and builds a strong case for the application of the precautionary principle, as it may in some situations avert the loss of human lives.

Per Professor Page, there is usually only one trial, either the hypothesis that there is some adverse effect holds or it does not.[29] The important issue then is, how should the regulator respond where there is no obvious symmetric chance mechanism from which to reason, and the adverse event is unlikely to occur. [30] A publication of the World Health Organisation’s (WHO) Regional Office states that “precaution has been at the heart of public health protection for centuries, and the PP is indeed related to acting under uncertainty, an increasingly common circumstance in these days.”[31]  

As per the statement, some states claim that to take action there has to be clear and convincing scientific proof of actual or threatened harm. The statement also refers to the reality of scientific uncertainty and how the argument asserted by those states makes no allowance for it. It has been established that scientific uncertainty is one of the core elements of the different definitions examined, insofar that the lack of scientific information or the existence of scientific uncertainty calls for the application of the PP.

The PP has been adopted within certain frameworks. For instance, although not expressly mentioned in the WTO Agreement on the Application of Sanitary and Phytosanitary Measures (SPS Agreement) 1995[32] or the General Agreement on Tariffs and Trade 1994 (GATT),[33] the WTO states that in the fields of food safety, plant and animal health protection the need for precautionary actions in the face of scientific uncertainty has long been widely accepted.[34] Dispute resolution is often conducted by the WTO Dispute Settlement Panels and then by appeal to the Appellate body. There is generally a different approach followed by the Panels and the Appellate body.[35] Academic Ilona Cheyne for instance, argues that panels tend to favour trade liberalisation objectives and to reject any measures they find may upset the stability of the multilateral trading system.[36] On the other hand, the Appellate body follows a more sensitive approach, which also provides some guidance on how the PP may be applied within the WTO framework.

In the EC-Beef Hormones Case,[37] the EC restricted import and sale of meat produced with growth hormones, which measure was challenged by the US and Canada. The EU relied on the PP, arguing that there was a suspected risk associated with the consumption of such meat. The Appellate Body found that the measure was not adequately supported by scientific risk assessment.[38] Additionally, it noted that the PP was reflected in the SPS Agreement, but that it did not override the specific obligations of the Agreement.[39] Moreover, In EC-Biotech[40] the Panel found that the precautionary principle could have a bearing on a Panel’s assessment on whether an SPS measure is based on a risk assessment as required under Article 5(1).  The PP therefore, is reflected throughout the SPS and forms part of its risk assessment mechanism. Nevertheless, it appears that it is not adequately recognised under the WTO framework. Scientific uncertainty may not be a temporary situation, as suggested by Art.5(7) and a proper application of the PP would mean that the measures may need to be more than just a provisional response. Lastly, under the definitions of the PP examined, the onus should be on the proponent of the action rather than on the Member State that seeks to regulate against it.

The precautionary principle also features in the Cartagena Protocol on Biosafety to the Convention on Biological Diversity (CPB) 2000.[41] Further, under Article 1, the objective of the CPB is, to regulate the transfer, handling and use of living modified organisms (LMOs), in accordance with Principle 15 of the Rio Declaration,[42] as also mentioned in the Preamble. The Protocol establishes a process of Advanced Informed Agreement, which ensures countries are provided with the information necessary to make informed decisions before agreeing to the import of such organisms to their territory.[43] The process includes risk assessment and decision-making procedures for the importers of LMOs. However, Article 10(6) of the Protocol states that “lack of scientific certainty due to insufficient relevant scientific information and knowledge, regarding the extent of the potential adverse effects of an LMO.. shall not prevent the Party of import, from taking a decision,.. in order to avoid or minimise such potential adverse effects.” Hence, the importer is able to ban or impose conditions on the import of an LMO if the evidence of a risk assessment is incomplete. It should be noted that, in comparison to the SPS there is no presumption of the measures taken to be provisional, nor is there a requirement on the regulator to seek further information on the adverse effects. The Protocol can therefore be deemed to encompass the main elements of the PP.

The legal status of the PP

As per the statement, some states have asserted they are not bound to take action in the absence of scientific certainty. The concept of precaution, as discussed earlier does not originate in the international platform, and only became known as the precautionary principle under German national law in 1976 (Vorsorgeprinzip). The legal status of the PP is important, as then States may be able to rely on it. A rule of customary law creates obligations for all states.[44] Therefore, whether or not states are bound under the PP depends on whether it has crystalised under customary international law.

The Statute of the International Court of Justice (ICJ), defines customary international law as “evidence of general practice accepted as law.”[45] A norm of customary law entails two elements. Firstly, the subjective element, which requires evidence of opinio juris sive necessitates, the subjective belief by states that the principle amounted to a legal obligation. [46] And secondly, the objective element, which requires consistent and uniform state practice. [47] The best indicators of state practice are instruments of international and domestic law, as examined earlier.  It can be said that the PP has a strong presence in international agreements, albeit in many different forms. Historically, the 1995 UN Fish Stocks Agreement[48] expressly adopted the precautionary approach as a general principle of the agreement under Article 6.[49] The most cited version of the PP being Principle 15 of the Rio Declaration, which also codified the precautionary approach for the first time at global level. As a source of international law, it amounts to ‘soft law,’ meaning that although non-legally binding, the instrument is persuasive or influential.

The PP was invoked before the ICJ in the Nuclear Tests[50] cases. Judge Weeramantry, in his dissenting judgment identified the PP as the solution to the evidential problem illustrated by that case,[51] and that it is gaining increasing support as part of international environmental law.[52] Moreover, after the Treaty on the European Union 1992 (TEU), the precautionary principle became a part of EU environmental law.  The European Court of Justice (ECJ) also found that the PP is one of the principles on which Community policy is based.[53] As a result, the EC has made several attempts to crystalise the principle in customary international law. The WTO cases as previously examined being relevant. In Beef-Hormones case, the EU sought to rely on the PP whereas, the US and Canada referred to it as a precautionary approach instead. The Appellate body stated that the PP awaits authoritative formulation and that whether it is a general principle of international law is less than clear.[54] Which finding was echoed in EC-Biotech that identified the PP’s status as unsettled.[55] Moreover, the US strongly disagreed with the idea of the PP to become a rule of international law, especially after considering that there is no uniform definition of such a principle.[56]

As examined earlier, the PP is relevant to several regulatory contexts. The PP is mentioned in biotechnology law in international level under the CPB, and is explicitly and implicitly endorsed in CITES. Another example being the 1985 Convention for the Protection of the Ozone Layer (Vienna Convention),[57] which presented the Parties as mindful of the precautionary measures  for the protection of the ozone layer which have already been taken at the national and international levels.[58] Some legal scholars therefore believe that the precaution satisfies the necessary elements to be a norm of customary law. Philippe Sands, for instance states that “there is certainly sufficient evidence of state practice to support the conclusion that.. it reflects a principle of customary law.[59] On the other hand, scholars like Birnie, Boyle and Redgwell do not recognise such a principle, citing the several diverse interpretations of the PP and the uncertainties associated with its application.[60]

The PP’s effect and limitations

Successful application of the PP involves a “better-safe than sorry” approach, which theoretically would significantly reduce adverse effects, while supporting the principle of sustainable development. In Soule’s view, regulators should sometimes prohibit environmentally risky technology even though the risk of harm is uncertain and even though economic or other factors may recommend otherwise.[61] Hence, scientific false negatives would be avoided, as for instance potentially harmful chemicals would be banned until proven safe. Nevertheless, the principle also has its costs and limitations. A criticism of the PP therefore, is that it blocks scientific and technological progress[62] and thus puts a halt on innovation.[63]  For example, innovative products would also be banned should any health effect of their use be uncertain, [64] which is very likely, considering that such products would be new and researchers would need a significant time-span to conclusively state they are harmless. Which is a goodargument on why some states, as in the statement may not follow the PP.

Another concern as to the application of the precautionary principle is its effect on economic welfare. Such a concern has been recognised from the earliest formulations of the principle. For instance, the Swedish Minister of the Environment in the guidance of the EPA 1969, stated that “all means must be exhausted with the aim of avoiding inconvenience to industry, while maintaining high protection.[65] Additionally, it should be noted that application of the precautionary principle is not limited to outright banning, but may also mean delaying a decision or shutting down a facility for instance. Academic Frank Cross contends that the PP is based on an illusion that actions have no consequences beyond those intended, and argues that efforts to eliminate any given risk will create new risks.[66] Restricting or banning a good or activity domestically would not eliminate the market demand for that product. Instead, consumers would shift from the banned good or activity to a substitute, which may be more hazardous than the original.[67] Consequently, the regulator should also consider any collateral risks that may arise as a result of the proposed regulations, when acting for the best interest of public health and the environment.

Conclusion

The PP has made significant progress since its early formulations in German and Swedish national law. It has been adopted as a guiding principle within the EU by the EC, and is enshrined in Art.191 TFEU. As a result, the PP benefits from enforcement under EU law. After considering the international agreements, national laws and judgments examined, we can conclude that there is some evidence of state practice regarding the incorporation of the PP in international environmental law. However, the fact that there is no single agreed definition, and that its versions are generally found to fit one of two distinct categories, weak or strong definitions, demonstrate that the meaning of the PP in international law is unclear. It can be argued that it is more similar to an approach, as contended by the US in WTO cases, and therefore, does not appear to have crystalised as a norm of customary international law. Nevertheless, it remains an emerging principle and plays an important role internationally, within the framework of certain agreements. Moreover, the statement appears to be correct, insofar that the argument asserted by those states does not make allowance for the reality of scientific uncertainty. However, such an argument may be justified, especially after considering the limitations of the PP identified. 

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[1] See ILC Report (2001) GAOR A/56/10, 383-5, ‘jurisdiction or control’ includes ships, aircraft, spacecraft and occupied territory.

[2] P Birnie, A Boyle, C Redgwell, International Law & the Environment, (Oxford: OUP, 2009), p.153

[3] ibid. & ILC Report (2001) GAOR A/56/10, 391, at [5].

[4] Article 2, ILC Report (2001) GAOR A/56/10, 387 paras[2]-[3].

[5] 35 AJIL 684 (1941)

[6] [1949] ICJ Rep. 4

[7] See n.2, p.154

[8] A. Dias, ‘Human Rights, Environment and Development: With Special Emphasis on Corporate Accountability,’ (2000), HDR Background Paper

[9] Which illustrates the importance of the precautionary principle. See E. Fisher, ‘Environmental Law as ‘Hot’ Law – an Introduction by the General Editor – Special Issue celebrating the 25th Anniversary of the Journal of Environmental Law’, (2013), 25 (3) JEL 347

[10] P. Ky, ‘Qualifications, Weight of Opinion, Peer Review and Methodology: A Framework for Understanding the Evaluation of Science in Merits Review Understanding the Evaluation of Science in Merits Review’, (2012), 24 (2) JEL 207

[11] L. Fisher, ’Reviews — The Precautionary Principle In The Twentieth Century: Late Lessons From Early Warnings’ (2003) 15 JEL (104) (1)1

[12] J.E. Hicky, V.R. Walker, ‘Refining the Precautionary Principle in International Environmental Law,’ (1994-1995), 14 Va. Envtl. L.J. 423 & See G. Jones, ‘The impact of environmental law on planning decision-making’, (2012),  JPEL 22

[13] M. Martuzzi, J.A. Tickner, The precautionary principle:  protecting public health, the environment  and the future of our children, (Copenhagen: World Health Organisation Regional Office for Europe, 2004), p.31

[14]M. MacGarvin, Late lessons from early warnings: the precautionary principle 1896–2000, (Copenhagen: European Environment Agency, 2001), p.15 and p.65

[15] P Sands and J Peel, Principles of International Environmental Law, (Cambridge: CUP, 2012), p.217

[16] ibid, p.217-18

[17] S Elworthy, J Holder, Environmental Protection: Text and Materials, (Cambridge: CUP, 1997) , p.15 & K.V. Moltke, ‘The Vorsorgeprinzip in West German Environmental Policy’, in Royal Commission on Environmental Pollution, Twelfth Report: Best Practicable Environmental Option, HMSO, Cm 310, 1987, p.57

[18] M. Martuzzi, J.A. Tickner, The precautionary principle:  protecting public health, the environment  and the future of our children, (Copenhagen: World Health Organisation Regional Office for Europe, 2004), p.67

[19] K. Steele, ‘The precautionary principle: a new approach to public decision-making?’ (2006) LPR 5(1) 19-31

[20] A. Dias, ‘Human Rights, Environment and Development: With Special Emphasis on Corporate Accountability,’ (2000), HDR Background Paper, p.13

[21]‘first, do no harm’,  a crucial element of the Hippocratic oath as taken by physicians.

[22] M. Martuzzi, J.A. Tickner, The precautionary principle:  protecting public health, the environment  and the future of our children, (Copenhagen: World Health Organisation Regional Office for Europe, 2004), p.67

[23] K. Steele, ‘The precautionary principle: a new approach to public decision-making?’ (2006) LPR 5(1) 19-31

[24] A. Dias, ‘Human Rights, Environment and Development: With Special Emphasis on Corporate Accountability,’ (2000), HDR Background Paper, p.13

[25]‘first, do no harm’,  a crucial element of the Hippocratic oath as taken by physicians.

[26] F.B. Cross, ‘Paradoxical Perils of the Precautionary Principle’, (1996), 53, Wash & Lee L. Rev. 851, Art. 2, at p.852 & R.V. Percival, ‘Who’s Afraid of the Precautionary Principle?’, (2005), 23 ELR,

[27] T.Page, ‘A Generic View of Toxic Chemicals and Similar Risks’, 7 ELQ Article.1, 1978, at p.220

[28]ibid. at p.219-20

[29]ibid.

[30] ibid.  at p.226 & See Appendix A

[31] Per Roberto Bertollini, M. Martuzzi, J.A. Tickner, The precautionary principle:  protecting public health, the environment  and the future of our children, (Copenhagen: World Health Organisation Regional Office for Europe, 2004), pp.6,10,49

[32] The WTO Agreement on the Application of Sanitary and Phytosanitary Measures (SPS Agreement) 1995

[33] General Agreement on Tariffs and Trade 1994

[34] WTO SPS Agreement Training, (2015), Module Chapter 8.2 The “Precautionary Principle <https://www.wto.org/english/tratop_e/sps_e/sps_agreement_cbt_e/c8s2p1_e.htm>

[35] ‘I. Cheyne, ‘The Use of the Precautionary Principle in WTO Law and EC Law’, (2006), 8 ELR 4, pp.257-77  & S.M. Cone, ‘The Asbestos Case and Dispute Settlement in the World Trade Organization: The Uneasy Relationship between Panels and the Appellate Body.’ 23 MJIL (2001)103-42.

[36] ‘I. Cheyne, ‘The Use of the Precautionary Principle in WTO Law and EC Law’, (2006), 8 ELR 4, pp.257-77 

[37] EC-Measures Concerning Meat and Meat Products, WT/DS26/AB/R, WT/DS48/AB/R,

[38] Appellate Body Report, EC, Measures Concerning Meat and Meat Products (Hormones), WT/DS26/AB/R, WT/DS48/AB/R,

[39] See n.71 [125]

[40] Panel Report, EC- Approval and Marketing of Biotech Products, WT/DS291, WT/DS292, WT/DS293,

[41] Cartagena Protocol on Biosafety to the Convention on Biological Diversity (CPB) 2000

[42] ibid. Preamble at [4]

[43] ibid.

[44] M.D. Evans, International Law, 4th Edition, (Oxford: Oxford University Press, 2014), p.100

[45] The Statute of the International Court of Justice, Art.38(1)(b)

[46] North Sea Continental Shelf Cases, ICJ Reps 1969,

[47] See n.81 at p.98 & See Nicaragua v. United States Of America C.J Reports 1986, p. 14

[48] United Nations Conference on Straddling Fish Stocks and Highly Migratory Fish Stocks, New York, 1995

[49] ibid. Article 6(1), “States shall apply the precautionary approach widely to conservation, management and exploitation of straddling fish stocks and highly migratory fish stocks in order to protect the living marine resources and preserve the marine environment.”

[50] French Nuclear Tests Case (New Zealand v. France)

[51] Dissenting Opinion of Judge Weeramantry, Nuclear Tests Case (New Zealand v. France), p.58

[52] ibid.

[53] Pfizer Animal Health SA v Council of the European Union Case T-13/99 at [114]-[115]

[54] Appellate Body Report, EC, Measures Concerning Meat and Meat Products (Hormones), WT/DS26/AB/R, WT/DS48/AB/R, at [123]

[55] Panel Report, EC — Approval and Marketing of Biotech Products, at [15], “Just as the Appellate Body found it unnecessary and imprudent to make a finding on the status of the precautionary principle in international law, this Panel also should have no need to address this theoretical issue”

[56] ibid. “Nonetheless, the United States notes that it strongly disagrees that “precaution” has become a rule of international law.  In particular, the “precautionary principle” cannot be considered a general principle or norm of international law because it does not have a single, agreed formulation.  In fact, quite the opposite is true: the concept of precaution has many permutations across a number of different factors.  Thus, the United States considers precaution to be an “approach,” rather than a “principle” of international law”

[57] The Vienna Convention for the Protection of the Ozone Layer 1985

[58] ibid. Preamble at [5]

[59] P Sands and J Peel, Principles of International Environmental Law, (Cambridge: CUP, 2012), p.279

[60] P Birnie, A Boyle, C Redgwell, International Law & the Environment, (Oxford: OUP, 2009), p.161

[61] E. Soule, ‘Assessing the precautionary principle in the regulation of genetically modified organisms’, (2002), IJB 4(1), 18–33

[62] Journal – Block on technology

[63] See for instance the Inquiry on GM foods and application of the precautionary principle in Europe,
Per Andrew Miller MP, Chair of the Science and Technology Committee, “GM technology potentially offers an array of benefits, but concerns are being expressed that it is being held back by misuse of the precautionary principle.

[64] “One consequence of this ‘neo-prohibitionist’ approach is that innovative products are banned under the precautionary principle. The sale of the two least hazardous recreational nicotine products – e-cigarettes and Swedish snus – are banned in many countries despite growing evidence that they can play an important role in reducing the smoking rate. <http://www.iea.org.uk/sites/default/files/publications/files/Free%20Market%20Solutions%20in%20Health.pdf>

[65] J Zander, The Application of the Precautionary Principle in Practice: Comparative Dimensions, (New York: CUP, 2010), P.155 & P.159

[66] Paradoxical perils of the Principle, p.925

[67] P.863 & p.865