¹ ITLOS, Seabed Disputes Chamber, Responsibilities and Obligations of States Sponsoring Persons and Entities with Respect to Activities in the Area, Advisory Opinion of 1 Feb. 2011, at para. 135, available at: http://www.itlos.org/fileadmin/itlos/documents/cases/case_no_17/adv_op_010211.pdf. Students of the precautionary principle will observe that the Tribunal in its decision refers to the ‘precautionary approach’ rather than the ‘precautionary principle’. Despite discussions as to what such semantics may mean, this article adopts the assumption that there is no material difference between ‘approach’ and ‘principle’.

² The Indus Waters Treaty 1960 between the Government of India, the Government of Pakistan and the International Bank for Reconstruction and Development, Karachi (Pakistan), 19 Sept. 1960, retroactively in force 1 Apr. 1960, available at: http://siteresources.worldbank.org/INTSOUTHASIA/Resources/223497-1105737253588/IndusWatersTreaty1960.pdf.

³ PCA, In the Matter of the Indus Waters Kishenganga Arbitration (Islamic Republic of Pakistan v. Republic of India), Partial Award of 18 Feb. 2013, at paras 223–7, available at: http://www.pca-cpa.org/showpage.asp?pag_id=1392. The Court rejected the argument that the term ‘necessary’ should be read in any way beyond its normal use: ‘The Court considers inapposite the concepts of necessity developed in international trade law, investment law and other special areas’ (at para. 397).

⁴ See Fisher, E., ‘Precaution, Precaution Everywhere: Developing a “Common Understanding” of the Precautionary Principle in the European Community’ (2002) 9(1) Maastricht Journal of European & Comparative Law, pp. 7–28.CrossRefGoogle Scholar

⁵ Schlag, P., ‘Rules and Standards’ (1985) 33 UCLA Law Review, pp. 379–430.Google Scholar

⁶ N. 2 above.

⁷ Indus Waters Kishenganga Arbitration, Partial Award, n. 3 above, at paras. 223–7.

⁸ Ibid., at para. 452.

⁹ PCA, In the Matter of the Indus Waters Kishenganga Arbitration (Islamic Republic of Pakistan v. Republic of India), Final Award of 20 Dec. 2013, paras 110–12, available at: http://www.pca-cpa.org/showpage.asp?pag_id=1392.

¹⁰ Ibid., at para. 112.

¹¹ See, e.g., Zander, J., The Application of the Precautionary Principle in Practice (Cambridge University Press, 2010)CrossRefGoogle Scholar, Ch. 5; and N. de Sadeleer, Implementing the Precautionary Principle Approaches from the Nordic Countries, EU and USA (Earthscan, 2006).

¹² Declaration on Environment and Development 1992, Rio de Janeiro (Brazil), 3–14 June 1992, Principle 15, available at: http://www.un.org/documents/ga/conf151/aconf15126-1annex1.htm.

¹³ Vienna (Austria), 22 Mar. 1985, in force 22 Sept. 1988, available at: http://ozone.unep.org/new_site/en/vienna_convention.php.

¹⁴ Paris (France), 22 Sept. 1992, in force 25 Mar. 1998, available at: http://www.ospar.org.

¹⁵ New York, NY (US), 9 May 1992, in force 21 Mar. 1994, available at: https://unfccc.int/essential_background/convention/items/6036.php.

¹⁶ See, e.g., Bodansky, D., ‘Deconstructing the Precautionary Principle’, in Caron, D.D. & Scheiber, H.N. (eds), Bringing New Law to Ocean Governance (BRILL, 2004), pp. 381–91.Google Scholar

¹⁷ See Art. 3 UNFCCC, n. 15 above, and the Preamble to the Convention on Biological Diversity (CBD), Rio de Janeiro (Brazil), 5 June 1992, in force 29 Dec. 1993, available at: http://www.cbd.int/doc/legal/cbd-en.pdf.

¹⁸ See also de Sadeleer, N., Environmental Principles: From Political Slogans to Legal Rules (Oxford University Press, 2002), pp. 156–61CrossRefGoogle Scholar; V. Heyvaert, ‘Facing the Consequences of the Precautionary Principle in European Community Law’ (2006) 31 European Law Review, pp. 185–206; and European Commission, Communication from the Commission on the Precautionary Principle, COM(2000)1. Resnik argues that the precautionary principle applies to plausible and serious threats: see Resnik, D.B., ‘The Precautionary Principle and Medical Decision Making’ (2004) 29 Journal of Medicine and Philosophy, pp. 281–99.CrossRefGoogle ScholarPubMed

¹⁹ See, in general, de Sadeleer, n. 18 above.

²⁰ See Fisher, E. & Harding, R., ‘The Precautionary Principle: Towards a Deliberative, Transdisciplinary Problem-Solving Process’, in Harding, R. & Fisher, E. (eds), Perspectives on the Precautionary Principle (Federation Press, 1999), pp. 291–98Google Scholar; and E. Fisher, Risk Regulation and Administrative Constitutionalism (Hart, 2007), pp. 40–2.

²¹ Stirling, A., ‘Risk, Precaution and Science: Towards a More Constructive Policy Debate: Talking Point on the Precautionary Principle’ (2007) 8(4) EMBO Reports, pp. 309–15CrossRefGoogle ScholarPubMed, at 314.

²² See, e.g., Fisher, E., ‘Drowning by Numbers: Standard Setting in Risk Regulation and the Pursuit of Accountable Public Administration’ (2000) 20(1) Oxford Journal of Legal Studies, pp. 109–30Google Scholar at 115–6; and Stirling, A., Renn, O. & van Zwanenberg, P., ‘A Framework for the Precautionary Governance of Food Safety: Integrating Science and Participation in the Social Appraisal of Risk’, in Fisher, E., Jones, J. & von Schomberg, R. (eds), Implementing the Precautionary Principle (Edward Elgar, 2006), pp. 284–315.Google Scholar

²³ S. Jasanoff, Science and Public Reason (Routledge, 2012), p. 133 (original emphasis).

²⁴ De Sadeleer, n. 18 above, at p. 150.

²⁵ On the question of risk, values and environmental law, see Pedersen, O.W., ‘Modest Pragmatic Lessons for a Diverse and Incoherent Environmental Law’ (2013) 33(1) Oxford Journal of Legal Studies, pp. 103–31.Google Scholar

²⁶ A particularly enlightened exposition of this argument is found in M. Douglas & A. Wildavsky, Risk and Culture: An Essay on the Selection of Technological and Environmental Dangers (University of California Press, 1982). An interesting endorsement of this approach is found in the decision of the European Court of Human Rights (ECtHR) in Hardy and Maile v. United Kingdom, Decision of 14 Feb. 2012 (Appl. no. 31965/07), at para. 228, where the Court observes ‘in any event, the [risk assessment] merely expressed one view on a situation which was capable of multiple differing opinions’.

²⁷ Jasanoff, n. 23 above; see also J.B. Wiener et al., The Reality of Precaution (Earthscan, 2011).

²⁸ Jasanoff, ibid.

²⁹ N. 15 above.

³⁰ Art. 6 of the Agreement for the Implementation of the Provisions of the United Nations Convention on the Law of the Sea of 10 December 1982 relating to the Conservation and Management of Straddling Fish Stocks and Highly Migratory Fish Stocks (1995 Fish Stocks Agreement), 4 Dec. 1995, New York, NY (US), in force 11 Dec. 2001, available at: http://www.un.org/Depts/los/convention_agreements/texts/fish_stocks_agreement/CONF164_37.htm.

³¹ For a closer examination of the relationship between the precautionary principle and cost–benefit analysis see Driesen, D.M., ‘Cost–Benefit Analysis and the Precautionary Principle: Can They be Reconciled?’ (2013) 43 Michigan State Law Review, pp. 771–826Google Scholar, who argues (at p. 790) that the reference in the UNFCCC ‘demands, not a balance between costs and benefits, but an effort to minimize the costs of whatever abatement targets countries agree to adopt’.

³² Art. 38 of the Statute of the International Court of Justice, available at: http://www.icj-cij.org/documents/index.php?p1=4&p2=2&p3=0&.

³³ See, e.g., Lepard, B.D., Customary International Law: A New Theory with Practical Applications (Cambridge University Press, 2010), p. 6.Google Scholar See also ICJ, Continental Shelf (Libya Arab Jamahiriya v. Malta), Judgment, ICJ Reports (1985), p. 13, at 29–30, para. 27, and ICJ, Military and Paramilitary Activities In and Against Nicaragua (Nicaragua v. United States of America), Merits, Judgment, ICJ Reports (1986), p. 14, at 97, para. 183.

³⁴ ICJ, Legality of the Threat or Use of Nuclear Weapons, Advisory Opinion, ICJ Reports (1996), p. 226, at 241–2, para. 29.

³⁵ ICJ, Armed Activities on the Territory of the Congo (Democratic Republic of the Congo v. Uganda), ICJ Reports (2005), p. 168, at 251–2, para. 244.

³⁶ See, in general, Schlüter, B., Developments in Customary International Law: Theory and the Practice of the International Court of Justice and the International ad hoc Criminal Tribunals for Rwanda and Yugoslavia (BRILL, 2010), at p. 3.Google Scholar

³⁷ Wiener, J.B., ‘Precaution’, in Bodansky, D., Brunnée, J. & Hey, E. (eds), The Oxford Handbook of International Environmental Law (Oxford University Press, 2007), pp. 597–612Google Scholar, at 601.

³⁸ ICJ, Pulp Mills on the River Uruguay (Argentina v. Uruguay), Judgment, ICJ Reports (2010), p. 14, at 71, para. 164.

³⁹ With Judge Palmer arguing that the norm involved in the precautionary principle ‘has developed rapidly and may now be a principle of customary international law relating to the environment’: Request for an Examination of the Situation in Accordance with Paragraph 63 of the Court's Judgment of 20 December 1974 in the Nuclear Tests (New Zealand v. France) Case, ICJ Reports (1995), Dissenting Opinion of Judge Sir Geoffrey Palmer, at p. 142; and Judge Weeramantry pointing out that the precautionary principle is ‘a principle which is gaining increasing support as part of the international law of the environment’: Dissenting Opinion of Judge Weeramantry, at p. 342. See also Opinion of Judge ad hoc Vinuesa in ICJ, Pulp Mills of the River Uruguay (Argentina v. Uruguay), Request for Indication of Provisional Measures, 13 July 2006: ‘In my opinion, the precautionary principle is not an abstraction or an academic component of desirable soft law, but a rule of law within general international law as it stands today’, at pp. 152–3.

⁴⁰ ECtHR, Tătar v. Romania, Decision of 27 Jan. 2009 (Appl. no. 67021/01), at para. 27. Since then, however, the Court has failed to build on this line of argument: see, e.g., ECtHR, Hardy and Maile v. United Kingdom, n. 26 above.

⁴¹ N. 1 above, at para. 135.

⁴² Prominent among these are Sands, P. & Peel, J., Principles of International Environmental Law, 3^rd edn (Cambridge University Press, 2012), at p. 228Google Scholar; and Cameron, J. & Abouchar, J., ‘The Status of the Precautionary Principle in International Law’, in Freestone, D. & Hey, E. (eds), The Precautionary Principle and International Law (Kluwer, 1996), pp. 29–52.Google Scholar See also Trouwborst, A., ‘The Precautionary Principle in General International Law: Combatting the Babylonian Confusion’ (2007) 16(2) Review of European Community and International Environmental Law, pp. 185–95Google Scholar; and Hey, E., ‘The Precautionary Concept in Environmental Policy and Law: Institutionalizing Caution’ (1992) 4 Georgetown International Environmental Law Review, pp. 303–7.Google Scholar

⁴³ EC Measures Concerning Meat and Meat Products, WTO Appellate Body (1997), WT/DS26/AB/R, at para. 227. Notwithstanding the fact that individual Member States have argued against the principle enjoying customary status (see Sand, P.H., ‘The Precautionary Principle: A European Perspective’ (2000) 6 Human & Ecological Risk Assessment, pp. 445–58.Google Scholar A similar claim was made by Hungary against Slovakia in ICJ, Gabčikovo-Nagymaros Project (Hungary v. Slovakia), Judgment, ICJ Reports (1997), p. 62, at para. 97.

⁴⁴ Sands & Peel, n. 42 above, at pp. 222–3, and C.E. Foster, Science and the Precautionary Principle in International Courts and Tribunals (Cambridge University Press, 2011), passim. However, the shifting of the burden of proof argument was rejected by the ICJ in the context of the Pulp Mills decision, n. 38 above, at para. 164.

⁴⁵ Fisher, n. 4 above.

⁴⁶ Ibid., at p. 8.

⁴⁷ N. 13 above.

⁴⁸ N. 14 above.

⁴⁹ Fisher, n. 4 above, at p. 14.

⁵⁰ P-M Dupuy, ‘Formation of Customary International Law and General Principles’, in Bodansky, Brunnée & Hey, n. 37 above, pp. 449–66, at 453. See also Goldsmith, J.L. & Posner, E.A., The Limits of International Law (Oxford University Press, 2005), at p. 25Google Scholar, arguing that ‘states frequently change their views about the content of customary international law’.

⁵¹ See Bodansky, D., ‘Customary (and Not So Customary) International Environmental Law’ (1995) 3 Indiana Journal of Global Legal Studies, pp. 105–19Google Scholar, at 115.

⁵² Ibid.

⁵³ Ibid., at p. 113, and Dupuy, n. 50 above, at p. 452, respectively. See also Bodansky, D., The Art and Craft of International Environmental Law (Harvard University Press, 2010), at pp. 197–9.Google Scholar

⁵⁴ See, e.g., Goldsmith & Posner, n. 50 above.

⁵⁵ See Birnie, P., Boyle, A. & Redgwell, C., International Law and the Environment, 3^rd edn (Oxford University Press, 2009), at p. 161.Google Scholar

⁵⁶ Jasanoff, n. 23 above, at pp. 134–5.

⁵⁷ N. 43 above, at para. 123 (original emphasis).

⁵⁸ ICJ, North Sea Continental Shelf (Federal Republic of Germany v. Netherlands), Judgment, ICJ Reports (1969), p. 3, at 41–2, para. 72.

⁵⁹ Dworkin, R., Taking Rights Seriously (Harvard University Press, 1978), p. 24.Google Scholar

⁶⁰ Taken to the extreme this would mean the term ‘principle of customary law’ is a misnomer. A principle cannot be a ‘principle of customary law’ – only rules can.

⁶¹ Schlag, n. 5 above.

⁶² Ibid., at p. 400.

⁶³ Ibid.

⁶⁴ Ibid., at p. 390.

⁶⁵ Ibid., at p. 402.

⁶⁶ See also Driesen, n. 31 above.

⁶⁷ Partial support for this is also found in N. MacCormick, Legal Reasoning and Legal Theory (Clarendon, 1978), Ch. VII. See also Dworkin (n. 59 above, at p. 27) who observes that ‘it is not always clear from the form of a standard whether it is a rule or a principle’.

⁶⁸ Schlag, n. 5 above, at pp. 405–7. Here we can forge a link with the concept of interpretative communities as this is developed by Stanley Fish: see in general S. Fish, Is There a Text in This Class (Harvard University Press, 1980), at p. 331, in which Fish argues that it is these communities rather than the text itself which produce meanings and that ‘all objects are made not found, and that they are made by the interpretive strategies we set in motion’.

⁶⁹ Fish, S., The Trouble with Principle (Harvard University Press, 1999), at p. 3.Google Scholar

⁷⁰ Bodansky (n. 53 above, at p. 199) observes: ‘If one were a government lawyer providing advice to policymakers, then relying on the purported norms of customary international environmental law as the basis of one’s predictions would constitute malpractice.’

⁷¹ This definition of customary rules is what Kelly terms the ‘empirical CIL [customary international law]’: see Kelly, J.P., ‘The Twilight of Customary International Law’ (2000) 40(2) Virginia Journal of International Law, pp. 449–544Google Scholar, at 454.

⁷² Ibid., at pp. 453–4.

⁷³ For a useful exposition see Roberts, A.E., ‘Traditional and Modern Approaches to Customary International Law: A Reconciliation’ (2001) 95 American Journal of International Law, pp. 757–91.Google Scholar For a similar approach see also Lepard, n. 33 above.

⁷⁴ Kelly, n. 71 above, at p. 454. For a forceful critique of the ‘modern’ approach, see D’Amato, A., ‘Trashing Customary International Law’ (1987) 81 American Journal of International Law, pp. 101–5.Google Scholar D’Amato argues that customary rules cannot arise out of declarations and statements and that these cannot be taken to supply the opinio juris requirement as this relates to the psychological element. See also Kelly (n. 71 above, at p. 451) who argues that under the ‘indeterminate and manipulative theory […] CIL [customary international law] is then a matter of taste’.

⁷⁵ Bodansky, n. 53 above, at pp. 195–6.

⁷⁶ Ibid.

⁷⁷ D’Amato (n. 74 above) is, for example, highly critical of the ICJ’s willingness to identify customary rules in the Nicaragua case (n. 33 above). For an intriguing approach see also ICJ, Gabčíkovo-Nagymaros Project (Hungary v. Slovakia), Separate Opinion of Vice President Weeramantry, ICJ Reports (1977), pp. 98–104.

⁷⁸ N. 38 above.

⁷⁹ Ibid., at para. 204. See also Knox, J., ‘The Myth and Reality of Transboundary Environmental Impact Assessment’ (2002) 96 American Journal of International Law, pp. 291–319Google Scholar, for a useful overview.

⁸⁰ Pulp Mills, n. 38 above, at para. 205.

⁸¹ See, e.g., Nuclear Weapons, n. 34 above, and Birnie, Boyle & Redgwell, n. 55 above, at p. 137.

⁸² Birnie, Boyle & Redgwell, ibid., at pp. 147–8.

⁸³ ILC, Draft Articles on Prevention of Transboundary Harm from Hazardous Activities, in Report of the International Law Commission on the Work of its 53^rd Session, UN GAOR, 56^th Session, Supp. No. 10, at 43, UN Doc. A/56/10 (2001), reprinted in (2001) 2 Yearbook of the International Law Commission, 26, available at: http://legal.un.org/ilc/texts/instruments/english/commentaries/9_7_2001.pdf.

⁸⁴ New York, NY (US), 21 May 1997, in force 17 Aug. 2014, available at: http://legal.un.org/avl/ha/clnuiw/clnuiw.html.

⁸⁵ Declaration of the United Nations Conference on the Human Environment, Stockholm (Sweden), 5–6 June 1972, Principle 21, available at: http://www.unep.org/Documents.Multilingual/Default.asp?documentid=97&articleid=1503.

⁸⁶ Rio Declaration, n. 12 above.

⁸⁷ Birnie, Boyle & Redgwell, n. 55 above, at pp. 148–50.

⁸⁸ A perhaps cynical explanation for this may be found in the fact that the ‘no-harm rule’ and the EIA obligations have by now been ‘confirmed’ as customary rules by the ICJ, whereas this is not (yet explicitly) the case for the precautionary principle.

⁸⁹ See to this effect Wolfrun, R., ‘Precautionary Principle’, in Beurier, J.P., Kiss, A. & Mahmoudi, S. (eds), New Technologies and Law of the Marine Environment (Kluwer, 2000), pp. 203–14.Google Scholar