We can only know approximately what an armed attack is. The next question is the quantity of activity needed to constitute an armed attack. It is not submitted here that more than one event of the type ‘armed attack’ is required to trigger the justification of self-defence; it is rather that the event ‘armed attack’ itself may have a quantitative threshold. In particular, it is asserted that that threshold is higher than that of the corresponding prohibition of threats or uses of force in Article 2(4).
79 Armed Activities (2005) supra note 26, Separate Opinion Kooijmans at 313–314 (para 28), Separate Opinion Simma at 337 (para 11); Thomas M. Franck, Terrorism and the right of self-defense, 95 American Journal of International Law (2001) 839–843 at 839–840; Jửrg Kammerhofer, The Armed Activities case and non-state actors in self-defence law, 20 Leiden Journal of International Law (2007) 89–113 at 99–101; O’Connell (2002) supra note 24 at 10; Randelzhofer (2002b) supra note 28 at 802 (MN 35); Stahn (2004) supra note 28 at 834, 836. See Section 2.4.1.
80 Stephen R. Ratner, Jus ad bellum and jus in bello after September 11, 96 American Journal of International Law (2002) 905–921 at 907–909. Especially egregious: Teplitz (1995) supra note 28 at 613–614, who bases his theory that the alleged assassination attempt on ex-President George Bush senior in 1993 constituted an armed attack on two steps: first he claims that the Charter’s language does not require a direct armed attack, i.e. an attack committed by the armed forces of a state. He does not ask whether it was done in such a way as to constitute an armed attack and in his second step simply assumes the result: ‘The attempt meets the basic definition of “aggression,” since it was the use of “armed force” against the “sovereignty . . . of another State . . .” ’ Teplitz (1995) supra note 28 at 615.
81 Jason Beckett, New war, old law: Can the Geneva paradigm comprehend computers?, 13 Leiden Journal of International Law (2000) 33–51 at 49–51.
Uncertainty in International Law 20
The majority of scholars82 as well as the International Court of Justice in Nicaragua hold that only acts ‘on a significant scale’83 qualify as armed attacks and that ‘frontier incidents’ are excluded. The significance is measured by reference to the prohibition of force: ‘not every use of force contrary to Art. 2(4) may be responded to with armed force.’84 The reference to Article 2(4) is made because the act in question seems to need to at least violate the prohibition of force to qualify as an armed attack. Self-defence is a justification for unlawful behaviour, an excep- tion to a prohibition. Not only does the behaviour purportedly in self-defence have to be justifiable (that is, fulfil the actus reus condition of the prohibition), but the act to which the defender responds needs to be illegal (not justified). If it were other- wise, one could defend against a perfectly innocent (legal) act. Second, if that were the case, one could legally use self-defence against measures of self-defence or enforcement actions under Article 42 of the UN Charter. The dichotomy of prohibitions and exceptions/justifications in law makes contrary positive regula- tion illogical (though not impossible); we will discuss this topic in more detail in Sections 2.4.1 and 2.5.1. This explains the reliance and response to ‘threat or use of force’ when writers look for a definition of ‘armed attack’; this explains why many conclude that ‘attack’ is something above and beyond ‘force’. The following will describe the legal situation according to the dominant doctrine and the proposed solutions to the problems that are perceived to result from this doctrine.
The phenomenon has been called a ‘gap’85 and, accordingly, this doctrine will be called the ‘gap theory’. The starting point for the proponents of this theory is the different wording in the two Charter provisions: if the Drafters use different words they mean different things, otherwise they would use identical words. The majority also assumes that the difference in terms means a difference in ‘gravity’, apparently in continuation of the analogy to the term ‘aggression’ and the Definition of Aggression described above (Section 2.2.2). Article 2 of that defin- ition is held to imply that certain acts ‘or their consequences are not of sufficient gravity’ to constitute an act of aggression.86 While that article may be a point of origin for the doctrine, a caveat above and beyond the doubts about the analogy of the two terms seems apposite.87 The Definition of Aggression establishes the
82 Donner (1995) supra note 28 at 180; Gill (1988) supra note 28 at 36; Klein (1964) supra note 28 at 179. See Randelzhofer (2002b) supra note 28 at 790 (MN 11); Kreò (1995) supra note 41 at 187 (FN 793) for lists of scholars supporting this contention. Against: Dinstein (2005) supra note 9 at 193 (minimal threshold required), 176; John Lawrence Hargrove, The Nicaragua judgment and the future of the law of force and self-defense. Appraisals of the ICJ’s decision: Nicaragua v. United States (Merits), 81 American Journal of International Law (1987) 135–143 at 139; Kersting (1981) supra note 28 at 141; Kreò (1995) supra note 41 at 194; Kunz (1947) supra note 19 at 878.
83 Nicaragua (1986) supra note 5 at 101 (para 191), 103–104 (para 195), 110 (para 210).
84 Randelzhofer (2002b) supra note 28 at 790 (MN 4).
85 For example by Miller (1985) supra note 29 at 54; Dinstein (2005) supra note 9 at 193.
86 Kersting (1981) supra note 28 at 141. Kersting does not believe, however, that this result may be transposed to the term ‘armed attack’.
87 Bowett (1958) supra note 11 at 192: ‘It is well recognised that an armed attack is by no means the only form of aggression, of imperilling a state’s rights’.
2.2.3 Self-defence 21
priority principle in Article 2 and in particular the Security Council’s unfettered power under Article 39 to determine the existence of, inter alia, an act of aggres- sion, in the exercise of which the Council might well find that an act does not constitute aggression.88
For the majority opinion, the arguments of the minority are efforts to close the gap. Albrecht Randelzhofer’s approach to this issue will be adopted here. Assume that a threat or use of force is ‘x’ and an armed attack is ‘y’. The majority’s position is that x<y; the minority’s position is that x=y. The gap may be closed by one of two methods: either by arguing that because y=2, x must equal 2, or because x=1, y must equal 1. In legal terms, according to the first approach
‘Art. 2(4) proscribes only the use of force on a substantial scale and with consider- able effect, i.e. just the kind considered an armed attack within the meaning of Art. 51.’89
[T]he second approach which, in order to close the gap between Arts. 2(4) and 51, does not regard ‘armed attack’ in Art. 51 as being restrictive, compared to ‘use of force’ in Art. 2(4) and thus permits self-defence by forcible means in response to any use of armed force.90
The first method of closing the gap is an interpretation of the general prohibition of the threat or use of force and therefore not within this chapter’s purview. Less fundamental and to some more readily acceptable as a matter of legal policy91 is the way in which the second group of scholars bridges the gap. It involves putting the two terms on the level of the general prohibition. Their main argument is – as mentioned above – that ‘as a matter of semantics, the term “armed attack”
includes the use of force irrespective of its intensity’92 and that a differentiation cannot be based upon the differing wording of the two provisions.
While the scholarly writing on the subject is focused on the above, two ambigu- ous paragraphs of the judgment on the merits in Nicaragua93 have given rise to controversy over the consequences that follow from perceiving a gap. The ques- tion that the Court set itself was framed in the following way (deliberately taken out of context and having the context quite deliberately taken out):
Similarly, it must now consider the following question: if one State acts towards another State in breach of the principle of non-intervention, may a third State lawfully take such action by way of counter-measures against the first State . . .? A right to act
88 For a similar conclusion: Gray (2008) supra note 6 at 182–183.
89 Randelzhofer (2002b) supra note 28 at 791 (MN 7).
90 Randelzhofer (2002b) supra note 28 at 791 (MN 8).
91 Randelzhofer (2002b) supra note 28 at 791–792 (MN 8).
92 ‘[s]emantisch erfaòt der Begriff “bewaffneter Angriff” Gewaltanwendung unabhọngig von ihrer Intensitọt’. Kreò (1995) supra note 41 at 188. Also: Franzke (1965) supra note 12 at 133;
Franzke (1966) supra note 45 at 146; Hargrove (1987) supra note 82 at 139; Kunz (1947) supra note 19 at 878.
93 Nicaragua (1986) supra note 5 at 110–111 (paras 210–211).
Uncertainty in International Law 22
in this way . . . would be analogous to the right of collective self-defence in the case of an armed attack, but both the act which gives rise to the reaction, and that reaction itself, would in principle be less grave. Since the Court is here dealing with a dispute in which a wrongful use of force is alleged, it has primarily to consider whether a State has a right to respond . . . going so far as to justify a use of force in reaction to measures which do not constitute an armed attack but may nevertheless involve a use of force.94
However, an ambiguous sentence a few lines below the quoted passage reads:
‘It might however be suggested that, in such a situation, the United States might have been permitted to intervene in Nicaragua in the exercise of some right analogous to the right of collective self-defence, one which might be resorted to in a case of intervention short of armed attack.’95 John Lawrence Hargrove is not alone in interpreting this as strongly suggesting that these acts may involve the use of force.96 While this passage has raised considerable confusion – is there some kind of distinction between ‘real’ self-defence and ‘light’ forceful countermeasures?97 – it is rather a storm in a teacup. The Court had at this point in the judgment concluded its deliberations on the applicable law on the use of force (paragraphs 183–201) and considered the prohibition of intervention and possible justifications for it (paragraphs 202–211). Three references to ‘inter- vention’ have been taken out of the above citation to show how much one must remove from this passage in order to come to the conclusion Hargrove and others have reached. The prohibition of intervention is not the prohibition of the threat or use of force, even though both can be violated at the same time by an inter- state use of armed force. Acts prima facie constituting intervention could be justi- fied if the fulfilment of the conditions of an exception can be shown and ‘self- defence’ may be one of those exceptions. Whatever the scope of that exception, it seems incorrect to assume that all acts that are justified interventions by virtue of an analogous right of self-defence against interventions are also justified threats or uses of force as self-defence under Article 51.98 In a nutshell, the Court was not talking about the use of force, even though it expressed this in a rather curious way. Also, the Court made its position perfectly clear in the next paragraph:
In the view of the Court, under international law in force today – whether customary international law or that of the United Nations system – States do not have a right of
‘collective’ armed response to acts which do not constitute an ‘armed attack’.99
94 Nicaragua (1986) supra note 5 at 110 (para 210).
95 Nicaragua (1986) supra note 5 at 110 (para 210).
96 Hargrove (1987) supra note 82 at 138; Dinstein (2005) supra note 9 at 195, for whom the dictum remains ‘baffling’.
97 Dahm (1962) supra note 28 at 50, 56–57; Verdross (1984) supra note 28 at 290 (para 472). Specific- ally against this construct: Randelzhofer (2002b) supra note 28 at 791 (MN 7).
98 All S are P. ≠ All P are S.
99 Nicaragua (1986) supra note 5 at 110 (para 211) (emphasis added), see also 127 (para 249).
2.2.3 Self-defence 23
The word ‘collective’ denotes no more than the fact that the Court had to decide a case brought before it and that individual self-defence was not claimed by the Respondent.100 The United States alleged that its actions vis-à-vis Nicaragua were justified as collective self-defence, because the latter had committed armed attacks against certain third states.
It is difficut to bring substantial evidence of a ‘gravity’ requirement to such an interpretation of the Charter.101 As long as an act is an armed attack the threshold of self-defence is reached; there are no indications that the terms of Article 51 demand a particular level of violence. However, there are no arguments to be gained from the Charter that would support the opposite result either. The use of different words remains and without further explanation we are left with the plain words and thus able only to produce further tautologies. The non-identity in the wording of ‘threat or use of force’ and ‘armed attack’ means only that they are not identical wording and the two norms are different. This does not necessitate that ‘armed attack’ is of greater gravity than ‘use of force’; it may simply mean that ‘armed attack’ is a special case of ‘threat or use of force’.
The majority’s best argument is a broad systematic or teleological interpret- ation of the Charter. Armed attacks are events of greater scale and effect, because the Charter does not want an escalation of tit-for-tat ‘border incidents’ into a fully fledged war with self-defence being claimed by both parties. If state A were to use force against B which did not amount to an armed attack, B cannot legally rise to the provocation and thus the law discourages games of ‘Escalanto’, where two adversaries ‘up the ante’ gradually until the stakes get too high to ‘fold’. The Charter wants to minimise the use of force; the peoples of the United Nations are determined ‘to save succeeding generations from the scourge of war’.102 However, this is not the place for a discussion of the Charter’s aims and goals. Some of these issues will be covered by Section 2.5.