1 C. Leben, ‘Hans Kelsen and the Advancement of International Law’, (1998) 9 EJIL 287, at 288.

2 Kelsen, H., ‘Autobiographie’, in Jestaedt, M. (ed.), Hans Kelsen Werke (2007), I, 29, at 77Google Scholar; see also, regarding his emigration to the United States in 1940, R. A. Métall, Hans Kelsen. Leben und Werk (1969), 107.

3 I have previously formulated a theory of international law along neo-Kelsenian lines in J. Kammerhofer, ‘Uncertainty in the Formal Sources of International Law: Customary International Law and Some of Its Problems’, (2004) 15 EJIL 523; J. Kammerhofer, ‘Unearthing Structural Uncertainty through Neo-Kelsenian Consistency: Conflicts of Norms in International Law’, 2005, www.esil-sedi.org/English/pdf/Kammerhofer.pdf; Kammerhofer, J., ‘The Benefits of the Pure Theory of Law for International Lawyers, or What Use Is Kelsenian Theory?’, (2007) 12 International Legal Theory 5Google Scholar.

4 In particular H. Kelsen, The Law of the United Nations: A Critical Analysis of Its Fundamental Problems (1950); H. Kelsen, Principles of International Law (1952); H. Kelsen, Reine Rechtslehre (1960). As a rule only one Kelsenian source will be given, even if he made the same point in many publications.

5 Section 1.1 will deviate from this rule and take Kelsen's interpretation of the UN Charter as an example for ‘fit’, because we have the law of the Charter as a concrete text.

6 This seems to be implied in L. Sucharipa-Behrmann, ‘Kelsens “Recht der Vereinten Nationen”. Welche Relevanz hat der Kommentar heute noch für die Praxis?’, in R. Walter, C. Jabloner, and K. Zeleny (eds.), Hans Kelsen und das Völkerrecht. Ergebnisse eines internationalen Symposiums in Wien (1.–2. April 2004) (2004), 21; contra, J. L. Kunz, Völkerrechtswissenschaft und Reine Rechtslehre (1923); J. L. Kunz, ‘The “Vienna School” and International Law’, (1934) 11 New York University Law Quarterly Review 370.

7 See Kelsen, Reine Rechtslehre, supra note 4, at iv; Allott, P., ‘Language, Method and the Nature of International Law’, (1973) 45 British Yearbook of International Law 1971 79, at 98Google Scholar.

8 Kelsen, Reine Rechtslehre, supra note 4, at 283–345 (Parts VI and VII).

9 See the use of the concept of collective security as an example within the ‘coercive order’ postulate, Kelsen, Reine Rechtslehre, supra note 4, at 38–41, or of the ‘general principles of law’, 1945 Statute of the International Court of Justice, Art. 38(1)(c), within the discussion of Esser's distinction between ‘norm’ and ‘principle’, H. Kelsen, Allgemeine Theorie der Normen (1979), 99, 266–7.

10 Kelsen, Principles of International Law, supra note 4, at 3–18, 403–28 (sections I.A and V.B.1–6).

11 ‘We need to ascertain whether the societal phenomena called law have common characteristics which distinguish them from other, similar, phenomena.’ Kelsen, Reine Rechtslehre, supra note 4, at 32. Unless noted otherwise, all translations are the present author's.

12 ‘[T]hat “law” and its equivalent expressions in other languages denote such diverse objects that they cannot be subsumed under a common term.’ Kelsen, Reine Rechtslehre, supra note 4, at 32.

13 Kelsen, supra note 9, at 3.

14 ‘Another feature common to societal orders designated as law is that they are coercive orders in the sense that they react to antisocial “facts”, especially to such human behaviour, by [prescribing] an evil – like the taking of life, health, freedom or economic or other goods. [They prescribe] an evil which ought to be inflicted upon its target against his will, if necessary using physical force, hence is inflicted as a coercive measure.’ Kelsen, Law of the United Nations, supra note 4, at 34.

15 Kelsen, supra note 9, at 77–8, 108.

16 Kelsen, Reine Rechtslehre, supra note 4, at 37–8.

17 The ‘sanction’ for failing that proof is nothing more than withdrawal of the label ‘legal order’ from that normative order. A. Rub, Hans Kelsens Völkerrechtslehre. Versuch einer Würdigung (1995), 230.

18 Kelsen, Principles of International Law, supra note 4, at 14.

19 Ibid., at 14–15 (emphasis added).

20 ‘A norm is a legal norm if it belongs to a legal order and it belongs to a legal order, if its validity is derived from the Grundnorm of that legal order.’ Kelsen, Law of the United Nations, supra note 4, at 32 (emphasis added). Contra, J. Raz, The Concept of a Legal System: An Introduction to the Theory of Legal System (1980), 77–85.

21 As others before him, most notably John Austin, had to do because they saw coercion (in some sense) as a defining characteristic of all law: J. Austin, The Province of Jurisprudence Determined (1954), 141–2. The difference between Austin's and Kelsen's theories cannot be overrated, and it is quite clear that Kelsen was not in any way an ‘Austinian’, as has sometimes been claimed. There are numerous differences, inter alia that for Kelsen subjects were not sub homine sed sub lege: Leben, supra note 1, at 288–9.

22 J. Bernstorff, Der Glaube an das universale Recht: Zur Völkerrechtstheorie Hans Kelsens und seiner Schüler (2001), 77.

23 Kelsen, Law of the United Nations, supra note 4, at 321.

24 Kelsen, Principles of International Law, supra note 4, at 18.

25 Ibid., at 19. Cf. his interpretation of UN Charter law under that aspect infra.

26 A. Verdross and B. Simma, Universelles Völkerrecht (1984), 907–12 (paras. 1342–1346).

27 Kelsen, Principles of International Law, supra note 4, at 23.

28 International Law Commission, Articles on Responsibility of States for Internationally Wrongful Acts 2001 (ARS 2001), Commentary, introduction to Part III, Chapter II ‘Countermeasures’, para. 1, in International Law Commission, Report of the International Law Commission on the Work of its Fifty-Third Session, UN Doc. A/56/10 (2001) 29, at 296, reprinted in J. Crawford (ed.), The International Law Commission's Articles on State Responsibility: Introduction, Text and Commentaries (2002), 281.

29 Kelsen, Principles of International Law, supra note 4, at 25.

30 Kelsen, H., ‘The Essence of International Law’, in Deutsch, K. W. and Hoffmann, S. (eds.), The Relevance of International Law: Essays in Honor of Leo Gross (1968) 85, at 86 (emphasis added).Google Scholar

31 Kelsen, Principles of International Law, supra note 4, at 25.

32 Article 50(1)(a) ARS 2001. H. Isak, ‘Bemerkungen zu einigen völkerrechtlichen Lehren Hans Kelsens’, in O. Weinberger and W. Krawietz (eds.), Reine Rechtslehre im Spiegel ihrer Fortsetzer und Kritiker (1988) 255, at 259.

33 Bernstorff, supra note 22, at 77.

34 Ibid., at 78–9.

35 D. Zolo, ‘Hans Kelsen: International Peace through International Law’, (1998) 9 EJIL 306, at 312.

36 ‘Without the so-called principle of “bellum justum” there is no international law’. H. Kelsen, ‘Völkerrechtliche Verträge zu Lasten Dritter’, (1934) 14 Prager Juristische Zeitschrift, col. 419, at 427.

37 Kelsen, Principles of International Law, supra note 4, at 58; Rub, supra note 17, at 230.

38 Rub, supra note 17, at 230.

39 Isak, supra note 32, at 260–1.

40 Kelsen, Law of the United Nations, supra note 4, at xvi; cf. Schachter's accusation of inconsistency: O. Schachter, ‘The Law of the United Nations’, (1951) 60 Yale Law Journal 189, at 190–3.

41 Kelsen, Law of the United Nations, supra note 4, at 727–35.

42 Ibid., at 735–7.

43 Ibid., at 727. Hubert Isak draws this consequence: ‘Mit der Verankerung eines absoluten Gewaltverbotes in Art 2 Ziff 4 der Satzung der Vereinten Nationen ist die Existenz eines allgemein anerkannten Grundsatzes des “gerechten Krieges” äußerst fragwürdig geworden.’ ‘The imposition of an absolute prohibition of the use of force in Article 2(4) UN Charter has made the existence of a generally recognized principle of “just war” highly questionable.’ Isak, supra note 32, at 258–9.

44 Kelsen, Law of the United Nations, supra note 4, at 727–31, 734.

45 Ibid., at 732–3.

46 Ibid., at 735.

47 Ibid.

48 Ibid.

49 Kelsen, Principles of International Law, supra note 4, at 46–7.

50 Ibid., at 60. It is questionable whether self-defence as it is shaped today is a measure of law enforcement, rather than of mere repulsion of an act irrespective of its legality. Cf. J. Kammerhofer, ‘Uncertainties of the Law on Self-Defence in the United Nations Charter’, (2005) 35 Netherlands Yearbook of International Law 2004 143 for an overview. See infra section 2.3.1.

51 Kelsen, Law of the United Nations, supra note 4, at 726.

52 Ibid., at 735.

53 Ibid., at 735–6.

54 Ibid., at 726.

55 Ibid., at 736 (emphasis added).

56 John Herz is highly sceptical whether international law really ‘fits’. J. H. Herz, ‘The Pure Theory of Law Revisited: Hans Kelsen's Doctrine of International Law in the Nuclear Age’, in S. Engel (ed.), Law, State and International Legal Order: Essays in Honor of Hans Kelsen (1964), 107, at 109–11. Cf. Rub, supra note 17, at 269 (‘verankert die UN-Charta . . . kaum unzweifelhaft das bellum-iustum-Prinzip’, ‘it is doubtful whether the UN Charter imposes the bellum justum principle’).

57 Kelsen, Principles of International Law, supra note 4, at 404.

58 ‘[N]ormative [systems] valid at the same time’, Kelsen, Reine Rechtslehre, supra note 4, at 329.

59 Ibid., at 330.

60 ‘If one speaks of a relationship of two normative systems, one must presuppose their contemporaneous validity. Once such a “relationship” has been assumed, their “duality” is essentially abandoned and it is recognized as interim [idea], which is resolved in the end in the unity of the “relationship”’. H. Kelsen, Das Problem der Souveränität und die Theorie des Völkerrechts. Beitrag zu einer reinen Rechtslehre (1920), 111.

61 Kelsen, Law of the United Nations supra note 4, at 328–9; Zolo, supra note 35, at 307–8.

62 It is less than certain, however, whether Kelsen can be called ‘neo-Kantian’ sensu stricto. To some extent the use of philosophical constructs serves a didactic function in Kelsen's writings – to demonstrate the result of his own presuppositions by reference to similar philosophical theories.

63 O. Höffe, Kants Kritik der reinen Vernunft: Die Grundlegung der modernen Philosophie (2003), 270.

64 Herbert Hart, however, points out that J. L. Mackie had told him that Kelsen's postulate of unity could best be taken from the unity of Kantian Raum. H. L. A. Hart, ‘Kelsen's Doctrine of the Unity of Law’, in H. L. A. Hart (ed.), Essays in Jurisprudence and Philosophy (1983) 309, at 322 n. 32, citing I. Kant, Kritik der reinen Vernunft (1st edn 1781 (A), 2nd edn 1787) (B)), A 25, B 39.

65 ‘The logical principle of genera, accordingly . . . presupposes a transcendental principle. In accordance with this principle, homogeneity is necessarily presupposed in the variety of phenomena . . ., because without it no empirical conceptions, and consequently no experience, would be possible.’ Kant, supra note 64, at A 652, B 680 (trans. John Miller Dow Meiklejohn).

66 ‘The unity of the epistemic point of view demands a monistic approach.’ Kelsen, supra note 60, at 123. Contra, S. Griller, ‘Völkerrecht und Landesrecht – unter Berücksichtigung des Europarechts’, in Walter, Jabloner and Zeleny, supra note 6, 83 at 87.

67 ‘[S]earching for subspecies to every species, and minor differences in every difference. For, were there no lower conceptions, neither could there be any higher.’ Kant, supra note 64, at A 656, B 684 (trans. John Miller Dow Meiklejohn).

68 The terms genus and species are used in the Kantian sense, not in the sense employed by biology: Höffe, supra note 63, at 270 n. 44. Cf. Griller, supra note 66, at 105.

69 Until the mid-1960s Kelsen held that norms themselves do not logically contradict each other, because they cannot be true or false, but the sentences purporting to describe a norm – a Rechtssatz – can be either true or false, because they can either correctly describe a norm that exists or not. Kelsen, Reine Rechtslehre, supra note 4, at 76–7, 209–11. See, however, the change of view due to the ‘normological turn’ described in section 2.2.

70 Kelsen, Reine Rechtslehre, supra note 4, at 210.

71 Ibid., at 329.

72 Kelsen, supra note 60, at 107–11, 113; Kelsen, Principles of International Law, supra note 4, at 419–23; Kelsen, Reine Rechtslehre, supra note 4, at 330–2.

73 Kelsen, Principles of International Law, supra note 4, at 422. For an excellent overview see Rub, supra note 17, at 463–70.

74 Hart, supra note 64, at 309–10.

75 ‘Any of these positive [delegating] norms presupposes a certain hypothesis on the relationship of these two normative systems.’ A. Verdross, Die Einheit des rechtlichen Weltbildes auf Grundlage der Völkerrechtsverfassung (1923), at 76; Kelsen, supra note 60, at 103.

76 Rub, supra note 17, at 457; Jestaedt, M., ‘Konkurrenz von Rechtsdeutungen statt Koexistenz von Rechtsordnungen’, in Brunkhorst, H. and Voigt, R. (eds.), Rechts-Staat. Staat, internationale Gemeinschaft und Völkerrecht bei Hans Kelsen (2008) 233, at 236–7Google Scholar.

77 ‘It can be said here that two different, completely independent normative systems can only exist when they are derived from two different, completely independent “sources” or principles, basic norms, i.e. not in any way derivable from each other or reducible to the other.’ Kelsen, supra note 60, at 107 (emphasis added).

78 ‘[The enterprise Pure Theory of Law] has reached its goal, if others consider it worthy of continuation.’ Kelsen, Reine Rechtslehre, supra note 4, at vii.

79 Ibid., at 31–59.

80 Raz, supra note 20. The present author agrees with Ota Weinberger that the stipulation of sanctions cannot be a peculiarity (‘Eigentümlichkeit’) of legal vis-à-vis other normative orders. O. Weinberger, Normentheorie als Grundlage der Jurisprudenz und Ethik. Eine Auseinandersetzung mit Hans Kelsens Theorie der Normen (1981), 53.

81 ‘“[L]aw” and its equivalent expressions in other languages denote such diverse objects.’ Kelsen, Reine Rechtslehre, supra note 4, at 32.

82 The main reason why Kelsen's theory is said to be neo-Kantian is the analogous adaptation of Kant's Kategorien as method of cognition, but not of reality, as Kant did in Critique of Pure Reason, Kant, supra note 64, at A 65–130, B 90–169, but of the Ought.

83 L. Wittgenstein, Philosophical Investigations (1958), paras. 66–67.

84 ‘Thus, if a moral order prescribes certain behaviour under certain circumstances, it also stipulates that the others ought to approve of the compliant behaviour of a certain human being and that non-compliant behaviour ought to be met by disapproval. . . . Through prescribing approval of compliant behaviour and disapproval of non-compliant behaviour the normative order authorizes the creation of individual categorical norms corresponding to the general hypothetical norms.’ Kelsen, supra note 9, at 37–8, 108; Kelsen, Reine Rechtslehre, supra note 4, at 39–40.

85 Contra: Kelsen, Reine Rechtslehre, supra note 4, at 324.

86 ‘A statute prescribes inter alia that a collegiate organ, in order to function, needs to be convened by its chairman, but also prescribes that it has to elect its own chairman. If one cannot interpret this norm to mean that the organ may convene through any arbitrary procedure in case there is no chairman, but only that even in this case the collegiate organ may only be convened by its chairman, then the collegiate organ cannot function lawfully, that is: as an application of the statute. . . . The statute simply has a nonsensical content. But this is not to be excluded, because laws are the work of humans.’ Kelsen, Reine Rechtslehre, supra note 4, at 255.

87 ‘In order to be objectively seen as legal norm, a norm has to be the subjective sense of an act [of will] . . . and has to stipulate a coercive act or be in a relevant connection to such a norm.’

88 Kelsen, supra note 9, at 111.

89 ‘[That] something ought or ought not to be cannot follow from whether something is or is not.’ Kelsen, supra note 9, at 5.

90 Kelsen, Reine Rechtslehre, supra note 4, at 215–21.

91 Kelsen, supra note 9, at 112–13.

92 For an approach that misunderstands Kelsen's approach in the related area of ‘spheres of validity’ as attempt at an empirical, pseudo-sociological classification see H. H. G. Post, ‘Classification of the Rules of International Law According to Spheres of Validity’, (1976) 7 Netherlands Yearbook of International Law 157.

93 ‘Sicher ist . . . eine pluralistische Konstruktion mit einem einheitlichen Rechtsbegriff vereinbar. Nur ist dieser Rechtsbegriff dann eben nicht durch die theoretisch bejahte Geltung, sondern faktisch-empirisch . . . definiert . . .’. ‘A pluralist construction is of course . . . compatible with a uniform concept of law. In this case, however, the term “law” is not defined through theoretical validity, but as empirical fact . . .’. Rub, supra note 17, at 454.

94 See Kelsen, supra note 9, at 169. Hans Kelsen's courage in radically departing from views held for half a century is remarkable. It shows that his theory was not ossified and that he was willing to revise a well-thought-out construct (cf. Kelsen, Law of the United Nations, supra note 4) and that he constantly thought about possibly revising his theory.

95 See supra note 69.

96 Kelsen, supra note 9, at 136–40.

97 H. Kelsen, ‘Recht und Logik, (1965) 12 Forum, 421–5, 495–500, reprinted in H. Klecatsky, R. Marcić, and H. Schambeck (eds.), Die Wiener rechtstheoretische Schule. Ausgewählte Schriften von Hans Kelsen, Adolf Julius Merkl, Alfred Verdross (1968) 1469–97.

98 Kelsen, supra note 9 at 178.

99 See Kelsen, supra note 60, at 76, 111.

100 ‘A conflict between two norms belonging to different normative orders . . . cannot be denied by claiming . . . that from the point of view of one normative order only the norms of this order are valid, so that in case of a conflict . . . the norm of the other order in conflict with the norm of the former order is not valid . . . or vice versa. Kelsen, supra note 9, at 169.

101 Kelsen, supra note 9, at 330.

102 ‘The contrary view is based on the assumption of the possibility of a conflict – interpreted as logical contradiction – between two normative orders valid for the same sphere. The realization that a conflict of norms is not a logical contradiction means that as a consequence of the principle of unity . . . my theory of the uniqueness of a normative order valid for a certain sphere must fall.’ Ibid., at 330 (emphasis added).

103 Contrary to the early Kelsen with similar arguments later brought forth by Kelsen: Hart, supra note 64, at 331–2.

104 Kelsen, Principles of International Law, supra note 4, at 414.

105 Cf. Rub, supra note 17, at 459–61.

106 Kelsen, Reine Rechtslehre, supra note 4, at 197.

107 Kelsen, supra note 9, at 206–7.

108 Kunz, Völkerrechtswissenschaft, supra note 6, at 81.

109 Hart, supra note 64, at 319.

110 For a similar argument see Rub, supra note 17, at 459.

111 Jestaedt, supra note 76, at 5.

112 See in particular Art I Proklamation [vom 27. April 1945 über die Selbständigkeit Österreichs], Staatsgesetzblatt 1945/1 and Art I Verfassungs-Überleitungsgesetz, Staatsgesetzblatt 1945/4.

113 § 1 Abs 1 Sperrgebietsgesetz 2002, Bundesgesetzblatt I 2002/38.

114 Kant, supra note 64, at A 42, B 59; Kelsen, Reine Rechtslehre, supra note 4, at 74; W. Karl, Vertrag und spätere Praxis im Völkerrecht (1983), 28–9.

115 Griller, supra note 66, at 92, 125; Hart, supra note 64, at 315; Rub, supra note 17, at 462.

116 ‘[L]egal positivism, which imparts upon the enunciation of human laws an illusory dignity’, 35 Acta Apostolicae Sedis (1943), 9–24, cited in G. Radbruch, ‘Nachwort-Entwurf’, in Gustav Radbruch. Rechtsphilosophie. Studienausgabe, ed. R. Dreier and S. L. Paulson (2003), 204, n. 30.

117 Recently, a much-publicized report on the reform of the Charter suggested that these two articles are outdated and ought to be revised (read: eliminated). High-level Panel on Threats, Challenges and Change, A More Secure World: Our Shared Responsibility, UN Doc. A/59/565, at 77 (para. 298).

118 See supra note 50.

119 Kelsen, Principles of International Law, supra note 4, at 60. Interestingly, he does not say so in the relevant chapter of his commentary on the Charter, Kelsen, Law of the United Nations, supra note 4, at 791–805.

120 Kammerhofer, supra note 50, at 201.

121 Kelsen, Law of the United Nations, supra note 4, at 725.

122 Ibid., at 726.

123 Ibid., at 729.

124 Ibid., at 733.

125 For a proposal for a constitutional text for a radically re-formed international law see P. Allott, Eunomia: New Order for a New World (2001), at xxxv–xl.

126 Kammerhofer, ‘Uncertainty in the Formal Sources of International Law’, supra note 3, at 548.

127 Ibid., at 538.

128 Kelsen, Principles of International Law, supra note 4, at 417–18; identical in substance: Kelsen, Reine Rechtslehre, supra note 4, at 222–3, 324–5.

129 See R. Walter, ‘Die Rechtslehren von Kelsen und Verdroß unter besonderer Berücksichtigung des Völkerrechts’, in R. Walter (ed.), Hans Kelsen und das Völkerrecht (2004) in Walter, Jabloner, and Zeleny, supra note 6, 37–49, for an excellent comparison of Kelsen's and Verdross's international law theories.

130 ‘[A]n objectively valid norm, anchored in the Kosmos of values’. A. Verdross, Die Verfassung der Völkerrechtsgemeinschaft (1926) 31.

131 Cf. ibid., at 42–3.

132 Kelsen, supra note 60, at 262, 282.

133 Verdross, supra note 130, at 32.

134 Ibid., at 43–4.

135 Kammerhofer, ‘Uncertainty in the Formal Sources of International Law’, supra note 3, at 533; A. Bleckmann, ‘Monismus mit Primat des Völkerrechts. Zur Kelsenschen Konstruktion des Verhältnisses von Völkerrecht und Landesrecht’, (1984) 5 Rechtstheorie 337, at 345.

136 Kammerhofer, ‘Uncertainty in the Formal Sources of International Law’, supra note 3, at 539–40.

137 Kelsen, supra note 9, at 2.

138 The tricky question of the status of ‘general principles of law’ in Art. 38(1)(c) of the ICJ Statute will be left aside here.

139 Rub, supra note 17, at 315.

140 Merkl, A. J., ‘Die Rechtseinheit des österreichischen Staates. Eine staatsrechtliche Untersuchung auf Grund der Lehre von der lex posterior’, (1918) 37 Archiv des öffentlichen Rechts 56Google Scholar, reprinted in Adolf Julius Merkl, Gesammelte Schriften I/1, ed. D. Mayer-Maly, H. Schambeck, and W. D. Grussmann (1993), 169 at 192.

141 G. E. Lessing, Nathan der Weise (1779), Act 4, Scene 4.

142 M. Koskenniemi, From Apology to Utopia: The Structure of International Legal Argument (1989).

143 J. Bernstorff, ‘Kelsen und das Völkerrecht: Rekonstruktion einer völkerrechtlichen Berufsethik’, in Walter, Jabloner, and Zeleny, supra note 6, 143 at 163; M. Rotter, ‘Die Reine Rechtslehre im Völkerrecht – eine eklektizistische Spurensuche in Theorie und Praxis’, in Walter, Jabloner, and Zeleny, supra note 6, 51 at 51–2.

144 Schachter, supra note 40; Sucharipa-Behrmann, supra note 6.

145 ‘Only indiscriminate dogmatism could pretend that a positive legal system is possible without [theoretical] assumptions.’ Kelsen, supra note 60, at vi. See J. L. Kunz, ‘The Theory of International Law’, (1938) 32 American Society of International Law Proceedings 23, for a discussion of the role of theory in international law.