¹ Weil, P, ‘Vers une normativité relative en droit international?’ (1982) 86 Revue général de droit international public 5Google Scholar, and P Weil, ‘Towards Relative Normativity in International Law?’ (1983) 77 AJIL 413.

² As Wittgenstein pointed out, using the concept of ‘game’, features of a natural concept can only bear very loose ‘family resemblances’ (‘Familienähnlichkeiten’) at best, and are hardly suitable for the classic Aristotelian rules of concept formation and definition. L Wittgenstein, Philosophical Investigations (2^nd edn, Blackwell, Oxford, 1967) 31–32.

³ Abi-Saab, G, ‘Cours Général de Droit International Public’ (1987) 207 Recueil des Cours de l'Académie de Droit international de la Haye (RdC) 9, 132Google Scholar; ÁM Bellido, ‘Soft law: mucho ruido y pocas nueces?’ (2004) 8 Revista Electrónica de Estudios Internacionales 1, 1, <http://www.reei.org/reei8/MazuelosBellido_reei8_.pdf> accessed 10 August 2009.

⁴ A Aust, Handbook of International Law (2^nd edn, CUP, Cambridge, 2010) 11.

⁵ D Thürer, ‘Soft Law’ in R Bernhardt (ed), Encyclopedia of Public International Law Vol IV (ELSEVIER, Amsterdam, 2000) 452, 454. For this difficulty, see also JK Levit, ‘A Bottom–Up Approach to International Lawmaking: The Tale of Three Trade Finance Instruments’ (2005) 30 Yale J of Int'l L125, 127 and D Shelton, ‘Normative Hierarchy in International Law’ (2006) 100 AJIL 291, 319.

⁶ As it is set out in art 38(1) of the Statute of the International Court of Justice, but see also the question of unilateral legal acts of States.

⁷ Similarly eg MA Fitzmaurice, ‘International Protection of the Environment’ (2001) 293 RdC 9, 125; AT Guzman, ‘The Design of International Agreement’ (2005)16 EJIL 579, 583–584; LF Damrosch and others, International Law. Cases and Materials (4th edn, West Group, St Paul, 2001) 34.

⁸ Opinions in the studies advocating the concept of soft law are varied ast to which of these two types the term ‘soft law’ can be applied. Some expressis verbis acknowledge both forms, eg Thürer (n 5) 456 or K Nagy, Nemzetközi jog [International Law] (Püski, Budapest, 1999) 48–52. Some only accept the existence of soft law (II), eg Weil (n 1) 414 or RR Baxter, ‘International Law in “Her Infinite Variety”’ (1980) 29 ICLQ 549. There are authors who seem only to receive type (I) of soft law with approval, eg Aust (n 4) 11–12 or Péter Kovács, Nemzetközi jog [International Law] (Osiris, Budapest, 2006) 80 and 154.

⁹ E Roucounas, ‘Engagements parallèles et contradictoires’ 206 (1987) RdC 9, 176; similarly D Shelton, ‘Introduction: Law, Non–Law and the Problem of “Soft Law”’ in D Shelton (ed) Commitment and Compliance. The Role of Non–Binding Norms in the International Legal Systems (OUP, Oxford, 2000) 4.

¹⁰ These two types of soft law cannot be dealt with according to one set of criteria. Those having attempted such notwithstanding, either did not come to more general conclusions or were forced to separate the two types of soft law later on, eg Thürer (n 5) 455–456.

¹¹ Law of parsimony, ie pluralitas non est ponenda sine necessitate (plurality should not be posited without necessity) attributed by many to one of the greatest English scholastics, William of Ockham, also applying to redundant terms and concepts in the process of description of a phenomenon.

¹² In the law of the European Union, the founding treaties explicitly recognize non–binding norms (eg recommendations) within the system of Community or Union norms, see eg art 249(5) of the EC Treaty (Treaty of Rome, as amended). However, in the European Union the notion of these non–binding norms does not cover the concept of international soft law on account of differences in their creation and regulative functions. For a general and extensive analysis, see L Senden, Soft Law in European Community Law (Hart Publishing, Oxford, 2004).

¹³ For a good survey on the variants of soft law, see Damrosch et al (n 7) 142–158; see also MI del Toro Huerta, ‘El fenómeno del soft law y las nuevas perspectivas del derecho internacional’ (2006) VI Anuario Mexicano de Derecho Internacional 513, 533–537. <http://www.bibliojuridica.org/estrev/pdf/derint/cont/6/art/art12.pdf> accessed 10 August 2009.

¹⁴ Eg Roucounas (n 9) 174–193; A Cassesse, International Law (OUP, [specify (latest) edition] Oxford, 2001) 160–161. [This is the first edition. The 2nd (latest) edition of 2005 is not available for me.]

¹⁵ See eg H Hillgenberg, ‘A Fresh look at Soft Law’ (1999) 10 EJIL 499; F Münch and H-K Ress, ‘Non–Binding Agreements’ in R Bernhardt (ed), Encyclopaedia of Public International Law Vol III (ELSEVIER, Amsterdam, 1997) 606, 606–612. To make distinction between traditional international conventions or binding legal agreements and non–legal (political or technical) agreements sometimes poses serious difficulties, see eg Aegean Sea Continental Shelf (Greece/Turkey) [1978] ICJ Rep 3, 39–44, paras 94–107, and Dispute concerning Access to Information under Article 9 of OSPAR Convention (Ireland /United Kingdom) Permanent Court of Arbitration (Final Award of 2 July 2003) 30, para 90, <http://www.pca–cpa.org/> accessed 22 May 2009, see also P-M Dupuy, ‘L'unité de l'ordre juridique international’ (2002) 297 RdC 9, 134–135, and Fitzmaurice (n 7) 126–128. A separate problem is why States enter into non–legal (soft law) agreements instead of concluding formal treaties, but this issue is sociological in nature, see AE Boyle, ‘Some Reflections on the Relationship of Treaties and Soft Law’ (1999) 48 ICLQ 901, 902–904. So, there are explanations for the use of soft law by States founded upon, but to be separated from the explanations for the existence of soft law. I am only dealing with the latter problem in this article.

¹⁶ Bellido (n 3) 13–15 and generally see A-M Slaughter, ‘International Law and International Relations’, (2000) 285 RdC 9, 96–121. But this group of non–legal norms is not recognized as soft law by eg Thürer (n 5) 454.

¹⁷ However, the virtual boundaries of international soft law can be pushed further and, in theory, extended to all the normative phenomena, including unwritten norms, which play some role in international relations. So Francioni regards ‘elementary considerations of humanity’ used by the International Court of Justice in the Corfu Channel judgment (1948) as soft law which can be therefore drawn from unwritten sources, F Francioni, ‘International “Soft Law”: a contemporary assessment’ in V Lowe and M Fitzmaurice (eds), Fifty Years of the International Court of Justice: Essays in Honour of Sir Robert Jennings (CUP, Cambridge, 1996) 167, 169.

¹⁸ In the literature, these two features of traditional international legal norms are emphasized as important from the perspective of describing soft law in its relation to ‘hard’ law, see eg Bellido (n 3) 2; Boyle (n 15) 901–902; L Senden, ‘Soft Law, Self–Regulation and Co-Regulation in European Law: Where Do They Meet?’ (2005) 9.1 Electronic Journal of Comparative Law 1, 23. <http://www.ejcl.org/91/issue91.html>, accessed 22 May 2009; F Capotorti, ‘Cours general de droit international public’ (1994) 248 RdC 9, 116. However, it would be difficult to share Zemanek's position that binding nature of a norm only signifies that the obligation is enforceable if not performed, see K Zemanek, ‘The Legal Foundations of the International System’ (1997) 266 RdC 9, 141.

¹⁹ There are many authors who treat international soft law as part of international law. See eg Guzman (n 7) 583 or A D'Amato and K Engel (eds), International Environmental Law Anthology (Anderson Publishing Co, Cincinnati, 1996) 55. Following the lead of the prototype theory developed within cognitive psychology, Peters and Pagotto treat soft law as law, because ‘soft law is in the penumbra of concept of the law’, A Peters and I Pagotto, Soft Law as a New Mode of Governance: A Legal Perspective (2006) 1, 12, <http://www.eu–newgov.org/database/DELIV/D04D10_Democracy_and_New_Modes_of_Governance.pdf> accessed 10 August 2009. Even Koskenniemi seems to use the expression of soft law as ‘special law’, Fragmentation of International Law: Difficulties arising from the Diversification and Expansion of International Law. A/CN.4/L.682, 13 April 2006, para 490.

²⁰ Guzman (n 7) 583–584.

²¹ Hillgenberg (n 15) 500; Bellido (n 3) 39.

²² AC Arend, Legal Rules and International Society (OUP, New York, 1999) 25.

²³ J Sztucki, ‘Reflections on International “Soft Law”’ in J Ramberg and others (eds), Festskrift till Lars Hjerner. Studies in International Law (Norstedts, Stockholm, 1990) 549, 573, as quoted by Toro Huerta (n 13) 544.

²⁴ U Mörth, Soft Law and New Modes of EU Governance—A Democratic Problem? (2005) 6. <http://www.mzes.uni–mannheim.de/projekte/typo3/site/index.php?id=476> accessed 10 August 2009.

²⁵ Senden (n 18) 24., L Senden, ‘Soft law and its implications for institutional balance in the EC’ (2005) 1 Utrecht Law Review (No. 2) 79, 81, similarly M Mendelson, ‘Formation of Customary International Law’ (1998) 272 RdC 155, 360.

²⁶ The boundaries of the international system of lawmaking are much more unstable anyway, compared to domestic law, and therefore the dividing line between law and non-law can be washed away and questioned more easily, see Dupuy (n 15) 135.

²⁷ Since the concept of soft law itself presupposes the paradigm of a more or less traditionally featured, somewhat separated and autonomous international law, I will, therefore, stay within these limits, and will not refer to theories which, nurtured by legal realism or based upon it, dissolve the traditional international law in general international normativity, although followers of soft law have borrowed several arguments from them, see eg the New Haven school, Arend (n 22) 76–88; JHH Weiler and AL Paulus, ‘The Structure of Change in International Law or Is There a Hierarchy of Norms in International Law?’ (Symposium, Part 2) (1997) 8 EJIL 545, 550 and 559; RA Falk, ‘Casting the Spell: The New Haven School of International Law’ (Book Review) (1995) 104 Yale Law Journal 1991; Peters and Pagotto (n 19) 8.

²⁸ Although, within a natural law framework, promising attempts could be made and a possible theory would not be inconceivable (basically supported by the concepts of promise, good faith and cooperation). In this setting do Witteveen and van Klink invoke Fuller's conceptual system of the principles of the inner morality of law, placing it into the framework of a variant of discourse theories and applying to international lawmaking. All this would lead to dismantling the existing system of international lawmaking and formal legal sources, W Witteveen and B van Klink, ‘Why Is Soft Law really Law? A Communicative Approach to Legislation’ (1999) RegelMaat (No. 3) 126–140. <chten.uvt.nl/bartvanklink/softlaw.pdf> accessed 3 July 2007. The adjective ‘soft’ may be losing its meaning in this new context since abandoning the presently recognized system of formal legal sources the mandatory character of soft law could be acknowledged.

²⁹ As is referred to by Fitzmaurice (n 7) 126.

³⁰ Guzman (n 7) 584; similarly Zemanek (n 18) 142.

³¹ A Halvorssen–J Hovi, ‘The Nature, Origin and Impact of Legally Binding Consequences: the Case of the Climate Regime’ (2006) 6 International Environmental Agreements: Politics, Law and Economics 2, 157, 169.

³² Guzman (n 7) 584.

³³ M Marcussen, ‘OECD Governance through Soft Law’ in U Mörth (ed), Soft Law in Governance and Regulation: An Interdisciplinary Analysis (Edward Elgar, Cheltenham, 2004) 103, 112.

³⁴ Mörth (n 24) 4.

³⁵ Some basic objections to the binary approach are set out by eg Peters and Pagotto (n 19) 6–9.

³⁶ The theory of ‘graduated normativity’ based upon these considerations ultimately may provide a theoretical framework for the existence of soft law. See U Fastenrath, ‘Relative Normativity in International Law’ (1993) 4 EJIL 305, 331–339 or Reisman's claims in D'Amato-Engel (n 19) 57–59. Nowadays, in the same or similar sense the term ‘relative normativity’ is also used, though this notion was originally applied and linked by Weil to the problem of soft law (II), Weil (n 1) 416–419, see also Fastenrath ibid 305–306, but see Shelton (n 5) 320.

³⁷ See eg E Riedel, ‘Standards and Sources. Farewell to the Exclusivity of the Sources Triad in International Law?’ (1991) 2 EJIL 58, 58; Zemanek also claims that the obligatory and non–obligatory distinction does not hold too much water in practice, Zemanek (n 18) 141.

³⁸ The theories of soft law which treat international soft law as part of international law (see above) do not need to use the ‘grey zone’ theory. They cannot furnish us with an acceptable definition for this extended concept of international law, and at the same time they are also bound to cope with the problem of drawing a line between non–law and law (this latter including soft law, as well) if they want to maintain an autonomous sphere for international law. So these theories, although inflating the concept of international law, paradoxically also have to apply binary approach, similarly to the traditional views. In the following I am principally dealing with the theories of soft law which do not consider soft law a part of international law.

³⁹ Levit (n 5) 191.

⁴⁰ Boyle (n 15) 913; see also Thürer (n 5) 453; Zemanek (n 18) 143; H Thierry, ‘L’évolution de droit international' (1990) 222 RdC 9, 75; JAP Ridruejo, ‘Le droit international à la veille du vingt et unième siècle: normes, faits et valuers’ (1998) 274 RdC 9, 61.

⁴¹ Levit (n 5) 191.

⁴² Weiler and Paulus (n 27) 554.

⁴³ See eg Damrosch et al (n 7) 34; Peters and Pagotto (n 19) 7; Levit (n 5) 127.

⁴⁴ In his excellent study, Ho analyses a specific example from the sociological perspective and explores the causes and motives for States to follow soft law norms, DE Ho, ‘Compliance and International Soft Law: why do countries implement the Basle Accord?’ (2002) 5 Journal of International Economic Law 647, 647–688; see also the studies addressing the same question in Shelton (n 9).

⁴⁵ Levit seems to find a simple (and somewhat extreme) solution to this problem, terminating the non–legal sphere of international normativity. She claims that apart from treaties and customary international law, ‘other international rules and norms reside in the catch–all category of international soft law’ Levit (n 5) 127.

⁴⁶ Mendelson has taken stock of the persistent difficulties in determining the existence of a international customary rule, Mendelson (n 25) 170–171.

⁴⁷ Peters and Pagotto (n 19) 12.

⁴⁸ Fitzmaurice (n 7) 131; Mörth (n 24) 8.

⁴⁹ Senden (n 18) 23; Thürer (n 5) 454; C McCrudden, ‘The New Concept of Equality’ (2003) 4 ERA–Forum (No. 3) 9, 13; Thierry (n 40) 74.

⁵⁰ Eg Thürer (n 5) 454.

⁵¹ Eg Guzman (n 7) 583.

⁵² Eg Ridruejo (n 40) 61 and Toro Huerta (n 13) 543.

⁵³ Thürer (n 5) 454; similarly Toro Huerta (n 13) 539.

⁵⁴ For similar conclusions, see Shelton (n 5) 321.

⁵⁵ Here, it may suffice to refer to the famous part of the 1986 Nicaragua judgment, where the International Court of Justice assessed the legal value of UN General Assembly resolutions in the context of the formation of customary law, Military and Paramilitary Activities in and against Nicaragua (Nicaragua v United States of America) (Merits) [1986] ICJ Rep 14, 99–100, paras 188–189, but see also Legality of the Threat or Use of Nuclear Weapons (Advisory Opinion) [1996] ICJ Rep 226, 254–255, paras 70–73.

⁵⁶ It is well–known that the International Convention on the Elimination of All Forms of Racial Discrimination (adopted 21 December 1965, entered into force 4 January 1969) 660 UNTS 195 drew on the United Nations Declaration on the Elimination of All Forms of Racial Discrimination (General Assembly Resolution 1904 (XVIII) of 20 November 1963); see also, eg the Convention on Early Notification of a Nuclear Accident (adopted 26 September 1986, entered into force 27 October 1986) 1439 UNTS 275, and the Convention on Assistance in the Case of a Nuclear Accident or Radiological Emergency (adopted 26 September 1986, entered into force 26 February 1987) 1437 UNTS 133; their content is based on the following two IAEA gudelines: ‘Guidelines for mutual emergency assistance arrangements in connection with a nuclear accident or radiological emergency’ IAEA Doc INFCIRC/310 (1984), and ‘Guidelines on reportable events, integrated planning and information exchange in a transboundary release of radioactive materials’ IAEA Doc INFCIRC/321 (1985). See also O Schachter, International Law in Theory and Practice (Martinus Nijhoff, Dordrecht, 1991) 85; Boyle (n 15) 904 and Shelton (n 5) 321.

⁵⁷ Boyle (n 15) 901.

⁵⁸ It is worth noting that there are attempts to use the legal principle of good faith to push non–legal norms into legal territories. The basic assumption is that international actors' expectations relating to non–legal commitments, grounded in good faith and depending on the circumstances of adoption of these norms may increase their normative strength to the extent that these norms themselves acquire legal or quasi–legal status. See eg Fitzmaurice (n 7) 128–129; Bellido (n 3) 23–25; Schachter (n 56) 100; Roucounas (n 9) 172–173.

⁵⁹ International Convention for the Suppression of Acts of Nuclear Terrorism (adopted 13 April 2005, entered into force 7 July 2007) (2005) 44 ILM 815. The references by legal rules have weaker forms which do not incorporate non–legal standards into treaties, but only turn these standards into a basis for treaty interpretation (n 63).

⁶⁰ For instance art 20(1) of the Treaty between the Czech and Slovak Federative Republic and the Federal Republic of Germany on Good Neighbourly Relations and Friendly Cooperation of 27 February 1992, 1900 UNTS 69, declares that the contracting parties shall comply, at the minimum, with the political obligations set forth in CSCE documents, in particular the Document of the Copenhagen Meeting of the Conference on the Human Dimension of CSCE of 29 June 1990, as legally binding obligations. For such references to extra–legal standards in international conventions concluded by Hungary with its neighbouring countries, see Kovács (n 8) 154 and 327; K Nagy, ‘“Soft law” jellegű szabályok Magyarország kisebbségi rendelkezéseket tartalmazó kétoldalú szerződéseiben’ [‘Norms of “Soft Law” Nature in Hungary's Bilateral Conventions Containing Provisions on Minorities’] Acta Juridica et Politica Szegediensis (2000) Tomus LVIII Fasc 28. 399, 403.

⁶¹ The number of the possible examples is much higher, see eg Shelton (n 5) 321.

⁶² Zemanek argues that international courts and tribunals frequently take non–legal instruments into account, therefore the distinction between binding and non–binding instruments makes little sense in practice, Zemanek (n 18) 141.

⁶³ There is a huge number of instances falling into this context where the preamble to an international convention refers to non–legal international instruments. On the other hand, there are weaker references incorporated into the provisions of international conventions alluding to non–legal norms which do not make these norms obligatory, but will open a path for their use during the interpretation of the provision. For such a weak reference, see eg art 13(2) and (3) of the Rotterdam Convention on the Prior Informed Consent Procedure for Certain Hazardous Chemicals and Pesticides in International Trade (adopted 10 September 1998, entered into force 24 February 2004) 2244 UNTS 337 which provide that in determining the environmental, health or other labelling requirements applicable to some classes of chemicals when exported relevant international standards shall be taken into account by the state parties. This is a weak reference, which can still establish the use of non-legal norms for interpretation. The strong and weak reference is not the same, although in both cases it is about a certain completion of the content of a treaty provision with the help of which it can be applied. When it comes to strong references, a certain non-legal norm is to be applied separately from or together with, but in both cases by the force of the provisions of the convention. In case of a weak reference pointing to a specific path of interpretation, however, an external factor (a non–legal rule) determines the scope of a treaty provision.

⁶⁴ Fastenrath (n 36) 312–315; see also Riedel (n 37) 11; Capotorti (n 18) 117; Zemanek (n 18) 141.

⁶⁵ For a starting point, see the statement of the International Court of Justice in Gabcikovo–Nagymaros Project (Hungary/Slovakia) (Judgment) [1997] ICJ Rep 7, 77–78, para 140, and also United States—Import Prohibition of Certain Shrimp and Shrimp Products (Appellate Body Report, AB–1998–4) WT/DS58/AB/R (adopted 6 November 1998) DSR 1998:VII, 2755, paras 130–131.

⁶⁶ U Fastenrath, ‘Relative Normativity in International Law’ (1993) 4 EJIL 1 305–340.

⁶⁷ See MW Janis and JE Noyes, Cases and Commentaries on International Law (2^nd edn West Group, St Paul, 2001) 588–589.

⁶⁸ EC Measures Concerning Meat and Meat Products (Hormones), (Appellate Body Report, AB-1997-4) WT/DS26/AB/R, WT/DS48/AB/R (adopted 13 February 1998) DSR 1998:I, 135, point VI; Balmer-Schafroth and others v Switzerland (Appl no 22110/93) Judgment of 26 August 1997, ECHR Rep 1997-IV, 25 EHRR 598, para 40.

⁶⁹ See art 8 of the Additional Protocol to the Convention on Human Rights and Biomedicine, concerning Biomedical Research (adopted 25 January 2005, entered into force 1 September 2007) CETS 195. For a similar provision see art 4 of the Additional Protocol to the Convention on Human Rights and Biomedicine, on Transplantation of Organs and Tissues of Human Origin (adopted 24 January 2002, entered into force 1 May 2006) ETS 186.

⁷⁰ Kasikili/Sedudu Island (Botswana/Namibia) (Judgment) [1999] ICJ Rep 1045, 1060 and 1064–1065, paras 20 and 30.

⁷¹ Shelton (n 5) 320.

⁷² Cassesse (n 14) 160; Fitzmaurice (n 7) 126; Aust (n 4) 11–12.