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date: 11 August 2020

Can Non-State Actors Mount an Armed Attack?

Abstract and Keywords

Article 2(4) of the UN Charter prohibits the use of force between States. In so doing, it addresses itself to a strictly interstate context and does not speak to the phenomenon of uses of force by non-state actors (NSAs). The question examined in this chapter is whether the exception to that prohibition—the right to use force in self-defence—is nevertheless responsive to the war-making capacity of NSAs. Otherwise put, is the definition of ‘armed attack’ in Article 51 of the UN Charter (and related customary international law) conditioned on the attacker being a state? In exploring this question, the chapter considers whether attribution is a necessary condition (in ratione personae terms) for the applicability of Article 51 by assessing the language of the Charter (including its travaux préparatoires), jurisprudence of the International Court of Justice, and state practice.

Keywords: non-state actor, self-defence, use of force, armed attack, UN Charter, attribution, aggression

I. Introduction

Article 2(4) of the UN Charter1 prohibits the use of force between states, but that prohibition does not ‘impair the inherent right of individual or collective self-defence if an armed attack occurs against a Member of the United Nations’.2 In its Charter incarnation, the prohibition of the use of force is situated in a strictly inter-state context, and does not speak to the phenomenon of uses of force by non-state actors (NSAs). The question examined in this chapter is whether the exception to that prohibition—the right to use force in self-defence—is nevertheless responsive to the war-making capacity of NSAs or whether it is limited to a snapshot of the right as it may have been conceptualized in the immediate aftermath of a global conflict between states. Otherwise put, is the definition of ‘armed attack’ in Article 51 of the UN Charter (and related customary international law) conditioned on the attacker being a state?3

(p. 680) On a cursory examination, the logic of the UN Charter might suggest that an armed attack to which states can respond with defensive force in reliance on Article 51 must be attributable to a state. This is because Article 2(4) of the UN Charter prohibits the threat or use of force against the territorial integrity or political independence of any state. Using defensive force against the base of operations of NSAs within a foreign host state’s territory, even if that defensive force only targets the NSAs which have launched an attack, still amounts to a violation of the host state’s territorial integrity. If Article 51 is to be a true exception to the prohibition on the use of force as set forth in Article 2(4) (and a circumstance precluding wrongfulness with respect thereto4), it should respond in some way to the violation of the host state’s territorial integrity. The legal mechanism which has traditionally been relied on to preserve an inter-state reading of Article 51, yet accommodate the need to respond to attacks by NSAs, is that of attribution. As will be examined in Section II, attribution is certainly a sufficient condition (in ratione personae terms) for the applicability of Article 51 of the UN Charter.

The difficulty, however, with an exclusively attribution-based definition of ‘armed attack’ is that it fails to account for recent uses of defensive force in response to attacks carried out by NSAs (which were not attributable to the host state on the basis of Article 3(g) of the UN Definition of Aggression5 or the ILC Articles on State Responsibility) that were widely accepted as legitimate by the international community. In addition, a definition of ‘armed attack’ that is limited to attributable force fails to respond to the security concerns of states which may be the victim of un-attributable armed attacks. Section III explores the extent to which attribution is a necessary element of the right to respond to armed attacks by NSAs with defensive force in foreign territory through an examination of: (III.A) the language of the UN Charter (and the travaux préparatoires); (III.B) the jurisprudence of the International Court of Justice (ICJ); and (III.C) state practice. Section III further considers whether there is an alternative framework (to that of attribution) available that preserves an inter-state reading of Article 51, consistent with the logic of the UN Charter, but which accommodates the security needs of states to defend themselves against armed attacks by NSAs.

(p. 681) II. Aggression and Attributable Attacks by Non-State Actors

While the use of armed force by NSAs has been the subject of increasing (perhaps overwhelming) academic attention, it is not an entirely modern phenomenon. The capacity and willingness of states to wage war by proxy, through reliance on fighters associated with, but outside the formal structures of the state, has long been a source of concern to the international community.6 Such ‘indirect’ use of force was addressed extensively during negotiation of the UN Definition of Aggression, finally adopted by the General Assembly in 1974.7 The Special Committee on the Question of Defining Aggression spent much time debating whether uses of force by NSAs, with which the state had some involvement, should be included in the definition of aggression.8 It was generally agreed that state involvement in the activities of NSAs would amount to a breach of the peace or an illegal intervention in the domestic affairs of another state.9 Western states, however, insisted that the ‘organization or instigation of or assistance or participation in’ attacks by NSAs should figure in the definition of aggression.10 The Soviet Union preferred to distinguish between aggression and indirect aggression,11 while members of the Non-Aligned Movement (NAM) raised objections to the concept of indirect aggression altogether.12

Representatives of NAM states were preoccupied with the relationship between the definition of aggression and the definition of ‘armed attack’ under Article 51 of the UN Charter. In particular, NAM states were concerned that a failure to limit the definition of aggression to direct state action raised the possibility of powerful states disingenuously accusing weaker states of acquiescing in or supporting armed bands operating from their territory to justify an aggressive use of force (under the guise of self-defence) against that weaker state.13 As a result, the proposed definition of aggression supported by NAM members expressly excluded the right to use force in (p. 682) self-defence, in reliance on Article 51 of the UN Charter, in response to ‘subversive and/or terrorist acts by irregular, volunteer or armed bands organized or supported by another State…’14 In general, Western states rejected NAM’s treatment of ‘aggression’ and ‘armed attack’ as coextensive,15 did not accept as a matter of principle that defensive force in reliance on Article 51 could not be used in response to armed attacks by armed bands,16 and argued that failing to include indirect aggression in the definition would encourage states to engage in wars by proxy, through active or passive support of NSAs.17

The compromise between these positions, which allowed the UN Definition of Aggression to be adopted by consensus, operated on several fronts. First, the definition was adopted for the purposes of guiding the Security Council in the exercise of its powers under Article 39 of the UN Charter18 and was independent of any agreement on the definition of ‘armed attack’ under Article 51. Secondly, in respect of indirect aggression, the position seems to have been to accept that acts of aggression could be carried out by NSAs, but to require their attributability. Article 1 of the UN Definition of Aggression defines aggression as ‘the use of armed force by a State against the sovereignty, territorial integrity or political independence of another State…’19 The use of armed force, however, need not be carried out by a state’s military forces: Article 3(g) of the UN Definition of Aggression provides that ‘sending by or on behalf of a State of armed bands, groups, irregulars or mercenaries, which carry out acts [amounting to aggression], or its substantial involvement therein’ also amounts to aggression.20 Article 3 is intended to provide a non-exhaustive list of acts that amount to aggression within the meaning of Article 1. As such, the ‘sending by or on behalf of a State of armed bands…, or…substantial involvement therein’ in paragraph (g) must be interpreted as a lex specialis threshold for (p. 683) attributing the acts amounting to aggression carried out by the armed bands to the state sending them,21 thereby maintaining the Article 1 requirement that an act of aggression be a ‘use of armed force by a State’.22 Indeed, proposals to minimize the level of state involvement required for NSA force to amount to an act of aggression, including ‘assistance to’, ‘knowing acquiescence in’, or ‘collaboration in’,23 were rejected in favour of the ‘sending by or on behalf of’ and ‘substantial involvement therein’ standard.24

The ICJ has implicitly linked the concepts of ‘aggression’ and ‘armed attack’ through its reliance on the UN Definition of Aggression to determine the legitimacy of a use of force in self-defence.25 At a minimum, the UN Definition of Aggression recognizes that acts of aggression can be carried out by NSAs (if attributable to a state), and the ICJ has consistently treated the Article 3(g) standard of ‘sending by or on behalf of’ as a basis for attributing those acts to states when determining the scope of the Article 51 right to use force in self-defence.26 As discussed later, however, the circumstances of those cases do not suggest that the definition of ‘armed attack’ is subject to all the same conditions as the definition of ‘aggression’. Nor should they, given that states did not accept that the concepts of ‘aggression’ and ‘armed attack’ are coextensive in their negotiation of the UN Definition of Aggression and left the definition of ‘armed attack’ to its Charter and customary international law development.

III. Non-Attributable Attacks by Non-State Actors

The fact that the UN Definition of Aggression restricts acts of aggression by NSAs to attributable force does not preclude the possibility that armed attacks might be (p. 684) un-attributable—although it does make clear that attribution is at least a sufficient condition for the applicability of Article 51 of the UN Charter (in ratione personae terms). The question remains whether it is a necessary one.

A. Article 51 of the UN Charter and the Travaux Préparatoires

While Article 2(4) is clearly the progeny of its World War parents, prohibiting inter-state uses of force, there is nothing in the language of Article 51 which restricts ‘armed attacks’ to attacks carried out by or on behalf of states.27 Nor does the negotiating history of the UN Charter suggest that such a restriction should be read into Article 51. The initial Dumbarton Oaks proposals contained no reference to self-defence28—it was only in San Francisco that states proposed to expressly include reference to a right of self-defence in the Charter. These proposals were concerned with the possibility of an ineffective Security Council and were principally focused on the interim rights and responsibilities of regional security organizations (eg under the Act of Chapultepec29). As a result, the right of self-defence was addressed in the US Diplomatic Papers under the headings ‘Regional Arrangements’ or the ‘Regional Problem’.30

Some initial proposals regarding the right of self-defence referred to ‘an attack by any State’ against a member state31—suggesting that attribution was at least (p. 685) implicitly contemplated by sponsoring states. Other proposals, however, were without regard to the source of the attack which triggered the right of self-defence.32 In any event, discussions in regard to these proposals, concentrated as they were on the continued availability of regional security arrangements, never focused on the source of the attack (state or non-state). Indeed, reference to an attack ‘by any State’ was dropped from later proposals. The two proposals which formed the basis of the final text of Article 51 each conditioned the right of self-defence on an armed attack (without specifying the source of any such attack) and the Security Council’s inaction (whether characterizing that inaction as a ‘failure’ or not).33 The move from an ‘attack by any State’ to ‘armed attack’ (without reference to its source) was not the subject of minuted discussion.34 While deletion of the words ‘by any State’ might be interpreted as supporting the argument that attribution is not a necessary condition of reliance on Article 51, it might also be the case that ‘by any State’ was considered implicit. Without any discussion of the change in language (and whether the change was intended to convey meaning)—the travaux préparatoires are at best ambiguous on this issue. And given that ambiguity, there is no interpretive basis for augmenting the language of Article 51 by reading in the words ‘by any State’ following ‘armed attack’.

B. The ICJ’s Jurisprudence

The ICJ’s decisions in Case Concerning Military and Paramilitary Activities in and against Nicaragua, Legal Consequences of the Construction of a Wall in the Occupied Palestinian Territory Wall, and Case Concerning Armed Activities on the Territory of (p. 686) the Congo (DRC v. Uganda) might be interpreted as limiting ‘armed attacks’ to uses of force by or attributable to a state.35 There is, however, an alternative interpretation of the Court’s decisions, informed by judicial economy, which does not condition the right to use defensive force in reliance on Article 51 of the UN Charter on the attributability of an armed attack. Such an interpretation does not treat the Court’s pronouncements as generally applicable statements of law, but rather as determinations made in reference to (and constrained by) very particular factual contexts and the submissions of the parties—mindful of and limited by the facts relating to the alleged armed attacks and responsive uses of defensive force addressed by the Court in its decisions.

A majority of the ICJ has consistently held that uses of defensive force against the state from whose territory NSAs operate, in response to an armed attack by those NSAs, would only be a legitimate exercise of rights under Article 51 of the UN Charter if the armed attack was attributable to the state in whose territory (and against which) defensive force was used. To situate these judgments within their proper factual context, two separate forms of the use of force in self-defence, in response to armed attacks by NSAs, must be distinguished. The first involves a use of force which only targets the NSAs and their bases of operation in the foreign (host) state’s territory. The second is where the use of force also, or perhaps only, targets the foreign host state from whose territory the NSAs operate. The fact that the ICJ has required armed attacks launched by NSAs to be attributable to the state from whose territory they were supported or operated could be understood as a direct consequence of the fact that, in each contentious case to come before the ICJ, the host state was the target of defensive force. The ICJ’s refusal to address the circumstances under which a state has a right to use force in self-defence against (and only against) NSAs, however much lamented in the separate opinions,36 would therefore be justified on the basis of judicial economy and the facts of each case and should not be read as precluding such uses of defensive force.

(p. 687) In Nicaragua, the ICJ considered whether US assistance to the Nicaraguan Contra forces37 amounted to a legitimate exercise of the right of collective self-defence. The US claimed to be acting (primarily) in defence of El Salvador, which was the victim of armed attacks by NSAs allegedly supplied with arms through Nicaragua (with the active support, or at the very least complicity, of the Sandinista government).38 The Contras did not use force against the NSAs attacking El Salvador. Instead, the Contras’ main target was Sandinista troops.39 The ICJ noted that, to defend El Salvador, the US might have arranged for a strong patrol force along El Salvador’s frontiers, and that ‘it is difficult to accept that [the US] should have continued to carry out military and paramilitary activities against Nicaragua if their only purpose was, as alleged, to serve as a riposte in the exercise of the right of collective self-defence.’40

Given that the US-supported Contras were directly targeting the Nicaraguan government and military, the circumstances under which a state could legitimately use force in response to armed attacks by NSAs against and only against those NSAs was not in issue. And the Court did not decide it. Instead, the Court had to consider the circumstances under which a state could legitimately respond to armed attacks by NSAs with a use of defensive force against the state from whose territory the NSAs were allegedly supported. And on this limited question, the Court held that the conditions for a legitimate use of defensive force were not met because the armed attacks by the NSAs were not attributable to the state against which defensive force was used (relying on Art 3(g) of the UN Definition of Aggression as a basis of attribution).41 The Court also held that Nicaragua’s alleged assistance to NSAs (in the form of provision of weapons and logistical support) did not in itself (p. 688) amount to an armed attack.42 As a result, the wrongfulness of the US use of force (through its support of the Contras) was not precluded on the basis of Article 51 of the UN Charter.

In the Wall advisory opinion, Israel submitted a written statement to the Court addressing questions of jurisdiction and justiciability, but did not participate in the oral phase of the proceedings. The Court therefore relied on Israel’s justifications of the wall as submitted to the Secretary-General and General Assembly—namely that construction of the wall was consistent with Article 51 of the UN Charter and Security Council Resolutions 1368 (2001) and 1373 (2001) which ‘recognized the right of States to use force in self-defence against terrorist attacks’.43 The Court held that ‘Article 51 of the Charter…recognizes the existence of an inherent right of self-defence in the case of an armed attack by one State against another State. However Israel does not claim that the attacks against it are imputable to a foreign State.’44 One interpretation of this statement might be that international law conditions the right to use force in self-defence on the attributability of an armed attack. But given that such a condition would be at odds with the Security Council resolutions in regard to 11 September 2001 which the Court draws on,45 and its subsequent decision in Armed Activities (discussed later), this interpretation is not very convincing. The Court should instead be understood to be merely reaffirming the very conditions for the applicability of Article 51 of the UN Charter. Article 51 serves to justify a use of force that would otherwise be prohibited by Article 2(4) of the UN Charter. As the Court considered the West Bank to be occupied territory, Israel’s construction of the wall could not engage the Article 2(4) prohibition which only applies as between sovereign states. As Article 2(4) is inapplicable, Article 51 is equally inapplicable. The Court’s refusal to genuinely engage with the justification of self-defence has subjected it to severe criticism,46 but is arguably defensible based on the occupied status of the Palestinian territories and the resulting availability of an alternative legal framework within which to assess Israeli conduct.

In Armed Activities, the ICJ held that the attacks carried out by NSAs against Uganda were ‘non-attributable to the DRC’ (on the basis of Art 3(g) of the UN (p. 689) Definition of Aggression),47 and that the legal and factual circumstances giving rise to a right to use defensive force were therefore not satisfied. In its decision, the Court emphasized that Uganda’s defensive measures were carried out against the DRC,48 particularly noting the fact that Ugandan military action was directed against towns and villages far removed from the border region from which anti-Ugandan rebels launched attacks.49 Again, the Court’s decision reflects the distinction discussed previously between defensive force legitimately used against the state from whose territory NSAs operate (which—according to the Court—would require that the armed attacks are attributable to the territorial state on the basis of Art 3(g) of the UN Definition of Aggression), and defensive force against NSAs within the territorial state, while expressly refusing to address the conditions under which the latter use of force would be legitimate. Indeed, given that Uganda’s defensive force targeted the DRC, the Court held that it had ‘no need to respond to the contentions of the Parties as to whether and under what conditions contemporary international law provides for a right of self-defence against large-scale attacks by irregular forces.’50 By leaving the legitimacy of defensive force against NSAs expressly open, the Court can be understood to be responding to critiques of its Wall advisory opinion, confirming that the question was not settled in that decision (or even backtracking to the extent that it subsequently considered the question to have been wrongly settled). The statement also highlights the Court’s judicial economy—namely, that the Court does not decide more than it needs to, and should not be understood to have done so.

Taken together, these interpretations of the Court’s decisions suggest that attribution is only a necessary condition for the applicability of Article 51 of the UN Charter if a use of defensive force is targeted against the state from whose territory NSAs operate. The Court’s decisions do not preclude uses of defensive force against (and only against) NSAs in foreign territory, in response to un-attributable armed attacks carried out by those NSAs.

C. State Practice

There is room—in the language of the UN Charter, travaux préparatoires, and the ICJ’s jurisprudence—for the right to use defensive force in foreign territory against NSAs which have launched an un-attributable armed attack. That said, the growing recognition of such a right has not been entirely linear—not least because (p. 690) translating the declarations and practice of states into the elements of customary international law is not often a straightforward exercise. This is particularly the case in the intensely political settings of the General Assembly and Security Council, where states may adopt legalistic arguments for political effect.51 In addition, individuals speaking on behalf of states are not necessarily legally trained (and therefore may not situate their comments within recognized legal frameworks) or are sometimes too well trained (profiting from the ambiguities of language to keep options open). These challenges certainly should not prevent the search for opinio juris—but suggest that any such interpretive exercise needs to proceed carefully and be sensitive to factual context.

At one end of the spectrum—where relatively clear support for a right to use defensive force in response to un-attributable armed attacks by NSAs is evident—there is Operating Enduring Freedom and the 2006 Israeli/Hezbollah conflict. In the case of Operation Enduring Freedom, the US-led coalition responded to the 9/11 terrorist attacks with force, in express reliance on Article 51 of the UN Charter.52 The right to do so was recognized in Security Council Resolutions 1368 (2001) and 1373 (2001) and by the majority of the international community.53 The armed attacks carried out by Al Qaeda were not attributable to Afghanistan or its de facto Taliban government,54 but states (and the Security Council) nevertheless situated the response within the Charter framework, in particular Article 51. While the use of force against the Taliban (rather than merely against the Al Qaeda source of the armed attacks) remains controversial and the subject of much debate,55 at the very least the 9/11-related practice suggests broad acceptance of a right to use force in response to un-attributable armed attack by NSAs in reliance on Article 51 of the UN Charter.

(p. 691) In July 2006, Israel launched a large-scale military campaign against Hezbollah in Lebanese territory. The campaign was in response to Hezbollah’s abduction of two Israeli soldiers and a number of rocket attacks they launched from southern Lebanon into northern Israeli towns. Not without some ambiguity, Israel claimed to be acting not against the territorial host state, but primarily against NSAs56 whose conduct was un-attributable to Lebanon.57 A majority of Security Council members, as well as the UN Secretary-General, recognized Israel’s right to defend itself.58 But the scale of Israel’s use of force in Lebanese territory, particularly as regards the destruction of all three runways at Beirut International Airport59 and the tragic number of civilian deaths,60 meant that all but one of the states recognizing Israel’s right to act in self-defence also characterized Israel’s use of force in July 2006 as disproportionate or excessive.61 By evaluating the use of defensive force on the basis of its proportionality—a criterion which limits the legitimate exercise of the right of self-defence—these states implicitly confirmed Article 51 of the UN Charter as the applicable framework for assessing the lawfulness of Israel’s response. The logical implication of such an evaluation is that un-attributable armed attacks by NSAs fall within the scope of Article 51.

At the other end of the spectrum are uses of defensive force which have an impact on regional peace and security and are broadly condemned on at least that basis—for instance, Israel’s response to the terrorist attack against a Haifa café by Islamic Jihad in 2003. Following the attack, Israel launched a guided missile attack in Syrian (p. 692) territory, targeting what it claimed to be Islamic Jihad’s base of operations.62 All but one state appearing before the Security Council condemned Israel’s response.63 Many states firmly situated their condemnation of both the terrorist attack in Haifa and the Israeli response within the broader framework of the Middle East peace process.64 Their expressions of condemnation were based on the effect both attacks would have on the implementation of the road map devised by the Quartet,65 which was released in between the attack in Haifa and Israel’s military campaign in Syria. Other states, characterizing the Israeli response as aggression, did not address allegations of Syrian complicity in terrorist activities from its territory, but made statements in support of Syria which suggested that they did not accept the factual basis on which Israel claimed to act in self-defence in Syrian territory.66 None of the delegations making presentations before the Security Council addressed the legality of defensive force specifically targeting terrorist bases in foreign territory given an inability to rely on that state to prevent armed attacks planned or launched from its territory. While the expressions of condemnation before the Security Council have been interpreted as an absence of general support for a wide right to use force against terrorist training camps in foreign territory,67 it is very difficult to extract any such opinio juris from the statements made.

More recently, Colombia conducted military operations against the Revolutionary Armed Forces of Colombia (FARC) training camp in Ecuador, two miles from the Colombian border.68 Colombia claimed to be acting in self-defence, and partly invoked Ecuadorian support for FARC as justification for its violation of Ecuadorian sovereignty.69 In response, the Organization of American States adopted a resolution recognizing every state’s right to defend itself, but positioning the right in the context of the principles of sovereignty and non-intervention. The resolution considered that Colombia’s incursion constituted ‘a violation of the sovereignty and territorial integrity of Ecuador and of principles of international law’70, for which Colombia issued an (p. 693) apology.71 The swift South American condemnations and Colombian apology, both of which took place in the broader context of the inter-American system, highlight the lack of a broad acceptance, on the facts, of Ecuadorian support for FARC.

In the middle of this spectrum are uses of defensive force in response to un-attributable armed attacks by NSAs that are supported by some segments of the international community and condemned by others, or are not the subject of any reaction at all. In such cases, the precise legal basis for support or condemnation is not clearly articulated (or is not articulated in legal terms), or the facts on the basis of which a right to use defensive force is claimed are contested.

For example, in response to the 1998 terrorist attacks on its embassies in Tanzania and Kenya, the US attacked terrorist training camps in Afghanistan and a pharmaceutical plant in Sudan. The US notified the Security Council of its use of force in self-defence. In particular, the US highlighted that its use of force was only directed against installations and training camps used by the Bin Laden organization and was ‘carried out only after repeated efforts to convince the Government of the Sudan and the Taliban regime in Afghanistan to shut these terrorist activities down and to cease their cooperation with the Bin Laden organization.’72 In effect, the US justification for a use of defensive force is based on a right to target NSAs in foreign territory where there is an inability to rely on the host states’ counterterrorism efforts. The US attack on the pharmaceutical plant in the Sudan was widely condemned—primarily based on an absence of evidence that it was used for anything other than civilian purposes.73 There was no similar condemnation of the use of force in Afghanistan, which was directed solely against Al Qaeda facilities, and not against the Taliban.74 The failure to condemn should not necessarily be viewed as indicating broad support for the US military operation in Afghanistan. But given the abundant state practice of expressly condemning notified uses of defensive force in letters to the Security Council, the muted reaction (most particularly of the League (p. 694) of Arab States and the NAM) to the US operation in Afghanistan is significant and certainly signals the beginning of the emerging consensus that uses of force specifically targeting non-state terrorist actors, in response to armed attacks they launch from foreign territory, is a legitimate exercise of the right of self-defence.

The examples of a claimed right to use defensive force examined earlier are consistently articulated in terms of an inability to rely on the host state to prevent its territory from being used as a base of operations from which NSAs launch armed attacks.75 Where the complicity or failure to prevent territory from being used as a base of NSA operations was broadly accepted as fact, states have expressed their support for the right to use defensive force in response to un-attributable armed attacks by NSAs. This was particularly the case in regard to Operation Enduring Freedom and the Israel/Hezbollah conflict. Having supported those uses of defensive force, states should not be understood to be rejecting a right to respond to un-attributable armed attacks in principle in later cases (eg in regard to Colombia’s use of force against FARC training camps in Ecuador) merely because they reject its invocation in the particular circumstances. But the range of reactions to such invocations certainly indicates that the parameters of the right to respond to un-attributable attacks by NSAs are still being worked out in practice.

D. Reconciling Defensive Force against Non-State Actors and the Inter-state Prohibition of Article 2(4)

Article 51 is one of the UN Charter exceptions to the prohibition on the inter-state use of force, as set forth in Article 2(4). If Article 51 is to truly excuse, or preclude the wrongfulness of, a use of force that is otherwise in breach of a state’s territorial integrity, Article 51 should respond in some way to the inter-state context of Article 2(4). The ICJ has consistently conditioned the legitimacy of defensive force against the state from which NSAs operate on the attributability of the armed attacks carried out by those NSAs. The Court has, however, never ruled out defensive force against (and only against) NSAs operating from foreign territory in response to un-attributable armed attacks. While state practice suggests support for the legitimacy of such a right in principle (as discussed previously), commentators continue to gravitate towards attribution as the fuel powering an inter-state reading of Article 51. But, if we understand that attribution is nothing more than a mechanism for ensuring that Article 51 speaks to the prohibition on the use of force against the territorial integrity or political independence of another state, an alternative to attribution which accommodates recent state practice and is consistent with the logic of the (p. 695) UN Charter emerges. That alternative is based on the customary international law requirement that defensive force be necessary.76

If a host state is doing everything possible to prevent its territory from being used as a base of attacks by NSAs, then a use of defensive force in that state’s territory (against NSAs) is simply not necessary. Instead, the matter should be addressed through cooperative arrangements with the host state. If, however, a state is complicit in its territory being used as a base of NSA operations (and is therefore unwilling to prevent its territory from being used as a base of terrorist operations), or is unable to prevent its territory from being so used,77 then a use of defensive force in response to armed attacks by NSAs is indeed necessary, and the unwillingness or inability accounts for the limited and targeted violation of the host state’s territorial integrity. A state’s complicity in the activities of NSAs operating from its territory, which threaten the security of other states, is an internationally wrongful act for which the complicit state bears responsibility.78 Similarly, states are under an obligation to cooperate in the prevention of at least terrorist activities from their territory.79 A refusal to cooperate, in circumstances where the host state is otherwise unable to prevent its territory from being used as a base of such activities, would equally amount to an internationally wrongful act for which the host state would bear responsibility.

Host state wrongfulness does not of course, in itself, justify a use of force that is otherwise inconsistent with Article 2(4) of the UN Charter. A use of defensive force is justified by virtue of an armed attack by NSAs under the terms of Article 51. But necessity is a condition for the lawfulness of any such use of defensive force. And necessity is established by virtue of the host state’s complicity or failure to cooperate—both of which are wrongful. This element of host state wrongfulness simultaneously meets the conditions for lawful self-defence and accounts for the breach of the host state’s territorial integrity. Effectively, where defensive force responds to non-state armed attacks, necessity serves as the bridge between Article 51 and the inter-state prohibition of the use of force in Article 2(4).

(p. 696) IV. Conclusion

The ever increasing military capacity of NSAs calls for a modern assessment of the definition of ‘armed attack’ and the conditions for lawful self-defence. As early as 1974, when the UN Definition of Aggression was adopted, states were mindful of the security threats posed by NSAs and were weary of restricting their right to respond to such threats through overly heavy reliance on an inter-state paradigm. As a result, states left the definition of ‘armed attack’ open to customary international law development, and state practice in the 21st century suggests that the attributability of armed attacks by NSAs is no longer (if ever it was) a necessary condition of the right to use force in self-defence. That said, the precise parameters of the right to respond to an armed attack by NSAs with a use of force in foreign territory are still being worked out in practice. While states are quick to invoke the ‘unwilling or unable’ doctrine in their justifications of defensive force against attacks by NSAs, the international community has, quite rightly, refused to accept this ‘ritual incantation of a magic formula’80 without evidence of host state wrongfulness as a measure of the necessity of the defensive force. Territorial integrity therefore remains a cornerstone of the international legal system—with the right to use force in foreign territory in response to an un-attributable armed attack by NSAs at the fault line of the Charter’s prohibition of the use of force in Article 2(4) and recognition of states’ security interests in Article 51.

Notes:

(1) UN Charter, 26 June 1945, 1 UNTS XVI.

(2) UN Charter, Art 51 (emphasis added).

(3) This chapter only addresses the definition of ‘armed attack’ and the conditions for the applicability of Art 51 of the UN Charter in terms of the identity of the attacker. Further elements of the definition of ‘armed attack’, including whether the use of force is of sufficient gravity to amount to an armed attack within the meaning of Art 51, are addressed in Jan Klabbers, ‘Intervention, Armed Intervention, Armed Attack, Threat to Peace, Act of Aggression, and Threat or Use of Force: What’s the Difference’, Chapter 22 in this volume. See also Military and Paramilitary Activities in and against Nicaragua (Nicaragua v. US), Merits, Judgment, ICJ Rep 1986, 14, para 195; Oil Platforms (Iran v. US), Judgment, ICJ Rep 2003, 161, para 51.

(4) See Art 21, Commentary to Part Two, Chapter I, Draft Articles on Responsibility of States for Internationally Wrongful Acts, with Commentaries in Report of the International Law Commission on the work of its Fifty-Third Session, A/56/10 (2001), 31 (hereinafter ‘ILC Articles on State Responsibility’).

(5) UN Definition of Aggression, GA Res 3314 (1974), Annex.

(6) See eg Czechoslovakia’s and the Philippine’s observations on the Dumbarton Oaks proposals, both of which suggest that ‘aggression’ should be defined (for the purposes of triggering the Security Council’s powers) to include supporting armed bands. Doc 2, G/14(b) (1 May 1945), United Nations Conference on International Organization Documents (UNCIO), vol III, 469 (Czechoslovakia); Doc 2, G/14(k) (5 May 1945), UNCIO, vol III, 538 (the Philippines).

(7) UN Definition of Aggression.

(8) See Report of the Special Committee on the Question of Defining Aggression, A/8019 (1970), paras 26–30.

(9) A/8019 (1970), para 127.

(10) See Report of the Special Committee on the Question of Defining Aggression, A/8719 (1972), App B, Section A.

(11) See A/8019 (1970), para IV.B(7).

(12) See Reports of the Special Committee on the Question of Defining Aggression, A/7620, paras 26–9, 62, and 69–72; A/8019 (1970), Annex I, para 7; A/8419 (1971), paras 27–8; A/8719 (1972), Section C.

(13) See A/7620 (1969), para 127.

(14) Draft proposal submitted by Colombia, Cyprus, Ecuador, Ghana, Guyana, Haiti, Iran, Madagascar, Mexico, Spain, Uganda, Uruguay, and Yugoslavia, A/AC.134/L.16 and Add.1 and 2, para 7 in Report of the Special Committee on the Question of Defining Aggression, A/9019 (1973), 9.

(15) See Special Committee on the Question of Defining Aggression, Third Session, vol II, A/AC.134/SR.67 (19 Oct 1970), 6 (UK); A/8019 (1970), para 69,

(16) See eg A/AC.134/SR.67 (n 15), 106–7 (UK), 7 (Japan). See further, A/8019 (1970), paras 27 and 128. See further Derek W. Bowett, Self-Defence in International Law (Manchester: Manchester University Press, 1958), 256–60 and Sean D. Murphy, ‘The Crime of Aggression at the International Criminal Court’, Chapter 24 in this volume for a discussion of the concepts of ‘aggression’ and ‘armed attack’.

(17) A/7620 (1969), para 128. See also Benjamin Ferencz, ‘A Proposed Definition of Aggression: By Compromise and Consensus’ (1973) 22 International and Comparative Law Quarterly 407, 419–21, for a summary of the debate.

(18) See Special Committee on the Question of Defining Aggression, Seventh Session, UN A/AC.134/SR.110–113 (18 July 1974), 39 (UK).

(19) UN Definition of Aggression, Art 1 (emphasis added). See Julius Stone, ‘Hopes and Loopholes in the 1974 Definition of Aggression’ (1977) 71 American Journal of International Law 224, 232.

(20) UN Definition of Aggression, Art 3(g).

(21) ‘Sending by or on behalf of a State’ is not a basis of attribution specifically set forth in the ILC Articles on State Responsibility, and therefore can be regarded as a lex specialis basis of attribution, although it closely tracks the attribution threshold in Art 8 of the ILC Articles.

(22) UN Definition of Aggression, Art 1 (emphasis added).

(23) See A/9019 (1973).

(24) In keeping with this negotiating history, the Court has not accepted assistance to or collaboration with NSAs as a basis for attributing their armed attacks to a state, focusing instead on the ‘sending by or on behalf of’ element of Art 3(g). Nicaragua, Merits, para 195. Indeed, in Armed Activities on the Territory of the Congo (DRC v. Uganda), Judgment, ICJ Rep 2007, 43, the Court did not even mention ‘substantial involvement’, focusing entirely on the ‘sending by or on behalf of’ standard. The resulting interpretation of Art 3(g) is that ‘substantial involvement’ qualifies ‘sending by or on behalf of’ and, having been interpreted restrictively by the Court, does not admit very much less than actual sending.

(25) See nn 37–50 and accompanying text.

(26) See Nicaragua, Merits, para 195; Armed Activities, Judgment, para 146, each as discussed in nn 41, 48, and 49 and accompanying text.

(27) See Legal Consequences of the Construction of a Wall in the Occupied Palestinian Territory, Advisory Opinion, ICJ Rep 2004, 136, Separate Opinion of Judge Higgins, para 33, questioning the ICJ’s having required that armed attacks be attributed to a state in its Nicaragua decision, given that there is nothing in the language of the Charter itself that restricts ‘armed attacks’ to uses of force by a state.

(28) See ‘Proposals for the Establishment of a General International Organization’, The Department of State Bulletin, vol XI, No 375 (1 Oct 1944), 368–74. There is nevertheless some suggestion in US materials relating to the United Nations Conference that some Dumbarton Oaks delegations had considered the right to use force in self-defence to be implicit in the proposed collective security framework. See eg Foreign Relations of the United States, Diplomatic Papers (1945), vol I, 776, 781.

(29) The Act of Chapultepec was a declaration of reciprocal assistance and US solidarity, adopted at the Inter-American Conference on War and Peace in 1945 (The Department of State Bulletin, vol XII, No. 297 (4 Mar 1945), 339) and formalized in the Inter-American Treaty of Reciprocal Assistance (21 UNTS 324 (9 Feb 1947)).

(30) See eg Foreign Relations of the United States (1945), vol I, 662–4, 674, 719.

(31) Foreign Relations of the United States (1945), vol I, 659 (emphasis added). See also ibid, 674. A separate (and informal) US proposal responding to Latin American concerns (and expressly mentioning the Act of Chapultepec) relied on ‘aggression’ as the trigger for the right of self-defence: ‘Should the Security Council not succeed in preventing aggression, and should aggression occur by any state against any member state, such member state possesses the inherent right to take necessary measures for self-defence’ (emphasis added). Foreign Relations of the United States (1945), vol I, 685–6, 691. Turkey also proposed that ‘it would be useful to insert in the Charter a provision justifying legitimate defence against a surprise attack by another state’ (emphasis added). Doc 2, G/14(e) (1 May 1945), UNCIO, vol III, 483.

(32) A UK proposal relied on ‘a breach of the peace’ as the trigger for the right of self-defence (Foreign Relations of the United States (1945), vol I, 699), while a French proposal was without reference to any trigger (other than Security Council inaction). The French proposal had member states reserving a ‘right to act as they may consider necessary in the interest of peace, right and justice’ in the event of Security Council deadlock. Doc 2, G/7(o) (21 Mar 1945), UNCIO, vol III, 385 (as discussed in Foreign Relations of the United States (1945), vol I, 691, 698).

(33) The proposals were (1) ‘Nothing in this Charter impairs the inherent right of self-defence, either individual or collective, in the event that the Security Council has failed to maintain international peace and security and an armed attack against a member state has occurred’ (Foreign Relations of the United States (1945), vol I, 705 (UK/US)); and (2) ‘Nothing in this Charter impairs the inherent right of self-defence, either individual or collective, if prior to undertaking the measures for the maintenance of international peace and security by the Security Council an armed attack against a member state occurs’ (at, 813 (USSR)). The second proposal was largely in keeping with the UK/US draft, but responded to the view that it would be better not to mention the possibility of Security Council failure (at 713, 836). See also the US’s formal proposal on self-defence, substantially in line with Art 51 as adopted. Doc 510 G/62 (23 May 1945), UNCIO, vol III, 635.

(34) Post-vote comments on the provision as adopted unanimously by the Fourth Subcommittee were principally regarding its consistency with regional security arrangements. See UNCIO, vol XII (Commission III; Security Council), 680–1 (statement by Colombia with which South American states associated themselves).

(35) Arguing that attribution is a necessary element of ‘armed attack’, see eg Antonio Cassese, ‘The International Community’s “Legal” Response to Terrorism’ (1989) 38 International and Comparative Law Quarterly 589, 596–9 (requiring attributability under the law of state responsibility, but, in line with the dissents in Nicaragua, describing state support and acquiescence in terrorism as a ‘grey’ area in the law that might form the basis of attribution); Pierluigi Lamberti Zanardi, ‘Indirect Military Aggression’ in Antonio Cassese (ed), The Current Legal Regulation of the Use of Force (Leiden: Martinus Nijhoff, 1986), 111, 112–16; Luigi Condorelli, ‘Les attentats du 11 septembre et leur suites: où va le droit international?’ (2001) 105 Revue Générale de Droit International Public 829, 838; Olivier Corten, ‘Opération “liberté immutable”: Une éxtension abusive du concept de légitime defence’ (2002) 106 Revue Générale de Droit International Public 51, 55. But see eg Thomas Franck, ‘Terrorism and the Right of Self-Defence’ (2000) 95 American Journal of International Law 839, 840; Sean D. Murphy, ‘Terrorism and the Concept of “Armed Attack” in Article 51 of the UN Charter’ (2002) 43 Harvard Journal of International Law 41, 50; Christopher Greenwood, ‘War, Terrorism and International Law’ (2003) 56 Current Legal Problems 505, 419–21; Carsten Stahn, ‘Terrorist Acts as “Armed Attack”: The Right to Self-Defence, Article 51(1/2) of the UN Charter, and International Terrorism’ (2003) 27 Fletcher Forum of World Affairs 35, 42.

(36) See eg Armed Activities, Judgment, Separate Opinion of Judge Simma, para 8; Separate Opinion of Judge Kooijmans, para 25.

(37) The ICJ held that the US was responsible for financing, training, and providing logistical support to the Contras (including the supply of weapons and intelligence as to Nicaraguan troop movements). Nicaragua, Judgment, paras 100–8.

(38) An affidavit attached to the US Counter-Memorial on jurisdiction declared that Nicaragua was providing El Salvador rebels ‘with sites in Nicaragua for communications facilities, command and control headquarters, training and logistics support[, that the] Government of Nicaragua [was] directly engaged with these armed groups in planning ongoing military and paramilitary activities conducted in and against El Salvador’, and that the Nicaraguan government supplied the rebels with arms through its territory. Nicaragua, Judgment, para 128. The Court focused principally on the allegations relating to arms traffic, and held that ‘it has not…been able to satisfy itself that any continuing flow [of arms] on a significant scale took place after the early months of 1981’, and that, in any event, it had not been proven that Nicaragua should be held responsible for any arms traffic (Judgment, paras 153–5).

(39) There were also numerous reports of attacks on non-combatants (Nicaragua, Judgment, para 113) and Nicaragua alleged a US-devised strategy for the Contras to attack ‘economic targets like electrical plants and storage facilities’ in Nicaragua (Judgment, para 105).

(40) Nicaragua, Judgment, para 156. The ICJ’s argument is effectively a commentary on the necessity of the US operation. See Louis B. Sohn, ‘The International Court of Justice and the Scope of the Right of Self-Defence and the Duty of Non-Intervention’ in Yoram Dinstein (ed), International Law at a Time of Perplexity: Essays in Honour of Shabtai Rosenne (Leiden: Martinus Nijhoff, 1989), 869, 874.

(41) Nicaragua, Judgment, para 195.

(42) Nicaragua, Judgment, para 195.

(43) Wall, Advisory Opinion, para 138.

(44) Wall, Advisory Opinion, para 139.

(45) See further Section III.C.

(46) See Christian J. Tams, ‘Light Treatment of a Complex Problem: The Law of Self-Defence in the Wall Case’ (2005) 16 European Journal of International Law 965; Sean D. Murphy, ‘Self-Defense and the Israeli Wall Advisory Opinion: An Ipse Dixit from the ICJ?’ (2005) 99 American Journal of International Law 62. But note that the ICJ’s opinion has been interpreted as at least implicitly recognizing a right to use force in self-defence against non-state terrorist actors in foreign territory, even though refusing to accept such a right as applicable in the circumstances based on the occupied status of the territory from which the terrorist attacks emanated. See Iris Canor, ‘When Jus ad Bellum Meets Jus in Bello: The Occupier’s Right of Self-Defence against Terrorism Stemming from Occupied Territories’ (2006) 19 Leiden Journal of International Law 29, 132.

(47) Armed Activities, Judgment, para 146. The Court did not elaborate on the standard of ‘sending of armed bands’ as a basis for attribution because it did not consider there to be ‘satisfactory proof of the involvement in [the attacks by anti-Ugandan rebel forces against Uganda], direct or indirect, of the Government of the DRC.’ Ibid.

(48) Armed Activities, Judgment, paras 118 and 147.

(49) Armed Activities, Judgment, paras 81–6.

(50) Armed Activities, Judgment, para 147.

(51) Consider eg US statements regarding the Turkish and Iranian rights to use defensive force in Iraqi territory in response to cross-border armed attacks by the PKK—supporting the Turkish efforts to protect their border while condemning the Iranian response as without justification whatsoever, and justifying the difference in treatment on the basis of Iran being an outlaw state. See Tom Ruys, ‘Armed Attack’ and Article 51 of the UN Charter (Cambridge: Cambridge University Press, 2010), 432–3.

(52) See eg Letter dated 7 October 2001 from the Permanent Representative of the United States of America to the United Nations addressed to the President of the Security Council, S/2001/946; Letter dated 9 October 2001 from the Permanent Representative of Belgium to the United Nations addressed to the Secretary-General, S/2001/967; Letter dated 24 October 2001 from the Chargé D’Affaires a.i. of the Permanent Mission of Canada to the United Nations addressed to the President of the Security Council, S/2001/1005; Letter dated 29 November 2001 from the Permanent Representative of Germany to the United Nations addressed to The President of the Security Council, S/2001/1127; Letter dated 17 December 2001 from the Permanent Representative of New Zealand to the United Nations addressed to the Secretary-General, S/2001/1193.

(53) See Ruys, ‘Armed Attack’ and Article 51 of the UN Charter, 435–6.

(54) See Kimberley N. Trapp, State Responsibility for International Terrorism (Oxford: Oxford University Press, 2011), 53–54.

(55) See Ruys, ‘Armed Attack’ and Article 51 of the UN Charter, 442–3. For a discussion of the right to use defensive force against terrorist host states, see Lindsay Moir, ‘Action Against Host States of Terrorist Groups’, Chapter 32 in this volume.

(56) Israel claimed that it ‘has repeatedly been compelled to act not against Lebanon, but against the forces and the monstrosity which Lebanon has allowed itself to be taken hostage by’, S/PV.5503 (31 July 2006), 4. Israel also suggested that Lebanon, Iran, and Syria were responsible for Hezbollah’s activities, but did not appear to be suggesting that Hezbollah’s attacks were attributable to any of those states for the purposes of a defensive use of force. See S/PV.5489 (14 July 2006), 6; Identical letters dated 12 July 2006 from the Permanent Representative of Israel to the United Nations addressed to the Secretary-General and the President of the Security Council, S/206/515 (in which Israel claimed that responsibility for the attacks lay with the government of Lebanon but tied that responsibility to the fact that the attacks were launched from Lebanese territory).

(57) See Ruys, ‘Armed Attack’ and Article 51 of the UN Charter, 453–4.

(58) See S/PV.5489 (14 July 2006), 9–17; S/PV.5493 (21 July 2006), 17; S/PV.5492 (20 July 2006), 3; S/PV.5498 (30 July 2006), 3.

(59) See BBC, ‘Israel Imposes Lebanon Blockade’, 13 July 2006, available at <http://news.bbc.co.uk/2/hi/middle_east/5175160.stm>.

(60) See BBC, ‘Q&A: Mid-East War Crimes’, 21 July 2006, available at <http://news.bbc.co.uk/2/hi/middle_east/5198342.stm>; Human Rights Watch, ‘Fatal Strikes; Israel’s Indiscriminate Attacks against Civilians in Lebanon’, available at <http://hrw.org/reports/2006/lebanon0806/>; Amnesty International, ‘Deliberate destruction or ‘collateral damage’? Israeli attacks on civilian infrastructure’, at <http://web.amnesty.org/library/print/ENGMDE180072006>.

(61) S/PV.5489 (14 July 2006), 9 (Argentina), 12 (Japan), 12 (UK), 13–14 (Tanzania considered Israel’s use of force as disproportionate without expressly characterizing Israel’s use of force as in self-defence), 14 (Peru), 15 (Denmark), 16 (Slovakia), 16 (Greece), 17 (France). The US is the only state to have explicitly recognized Israel’s right to defend itself without characterizing Israel’s defensive measures as disproportionate or excessive. The Secretary-General also condemned Israel’s excessive use of force: S/PV5492 (20 July 2006), 3; S/PV.5498 (30 July 2006), 3.

(62) S/PV.4836 (5 Oct 2003), 5.

(63) See S/PV.4836 (5 Oct 2003). Only the US did not condemn the Israeli attack, and instead admonished Syria for ‘harbouring and supporting the groups that perpetrate terrorist acts’ (at 13–14). The Secretary-General also condemned the Israeli response in Syria, while also condemning the preceding terrorist attack in Haifa: SG/SM/8918 (2003).

(64) S/PV.4836 (5 Oct 2003), 9 (Spain, China, UK, Russia), 10 (France, Bulgaria), 11 (Chile, Mexico), 12 (Angola, Guinea), 13 (Cameroon). But see ibid, 14 (League of Arab States).

(65) In April 2003, the United Nations, European Union, the US, and Russia (the ‘Quartet’) presented a ‘performance-based roadmap to a permanent two-state solution to the Israeli-Palestinian conflict’ to Palestinian and Israeli leaders. See <http://www.un.org/News/dh/mideast/roadmap122002.pdf>.

(66) S/PV.4836 (5 Oct 2003), 15 (Lebanon), 16 (Algeria), 18 (Egypt), 19 (Tunisia), 19–20 (Kuwait), 20 (Saudi Arabia), 21 (Iran), 22 (Bahrain), 23 (Libya, Yemen), 24 (Qatar).

(67) See Christine Gray, International Law and the Use of Armed Force (3rd edn, Oxford: Oxford University Press, 2008), 237.

(68) (March 2008) 54 Keesing’s Record of World Events 48456.

(69) (March 2008) 54 Keesing’s Record of World Events 48456.

(70) OAS, Convocation of the Meeting of Consultation of Ministers of Foreign Affairs and Appointment of a Commission, 5 Mar 2008, CP/RES.930 (1632/08).

(71) Speech of Colombian Ambassador to OAS, 4 Mar 2008, available at <http://www.oas.org/speeches/speech.asp?sCodigo=08-0021>.

(72) Letter dated 20 August 1998 from the Permanent Representative of the United States of America to the United Nations addressed to the President of the Security Council, S/1998/780.

(73) The Sudan, in a letter to the Security Council, denied that the pharmaceutical plant in Khartoum was used for terrorist purposes. Letter dated 21 August 1998 from the Permanent Representative of The Sudan to the United Nations addressed to the President of the Security Council, S/1998/786. The League of Arab States and Non-Aligned Movement condemned the US for its attack on the Sudan. Letter dated 21 August 1998 from the Charge D’Affaires A.I. of the Permanent Mission of Kuwait to the United Nations addressed to the President of the Security Council, S/1998/789; Letter dated 24 August 1998 from the Charge D’Affaires A.I. of the Permanent Mission of Kuwait to the United Nations addressed to the President of the Security Council, S/1998/800; Letter dated 21 September 1998 from the Permanent Representative of the Sudan to the United Nations Addressed to the President of the Security Council, S/1998/879.

(74) The US position at the time was that Al Qaeda operated on its own, without having to depend on a state sponsor for support (although depending on state acquiescence). See Sean D. Murphy (ed), ‘Contemporary Practice of the United States’ (2000) 94 American Journal of International Law 348, 367.

(75) See Kimberley N. Trapp, ‘Back to Basics: Necessity, Proportionality, and the Right of Self-Defence against Non-State Terrorist Actors’ (2007) 56 International and Comparative Law Quarterly 141, 147–55; Ruys, ‘Armed Attack’ and Article 51 of the UN Charter, 494–5.

(76) For a discussion, see Olivier Corten, ‘Necessity’, Chapter 39 in this volume.

(77) In regard to the Israel/Lebanon 2006 war, states which recognized Israel’s right to defend itself also underlined the need for Lebanon to extend its exclusive control over all of its territory and to act in prevention of Hezbollah’s attacks against Israel (S/PV.5489 (14 July 2006), 9–17. See also S/PV.5492 (20 July 2006), 4; SC Res 1559 (2004), paras 1–3; SC Res 1583 (2005), paras 3–4; SC Res 1655 (2006), paras 3, 6, 8; SC Res 1680 (2006), preamble; and SC Res 1701 (2006), para 3). By accepting a right to use defensive force in response to attacks by NSAs, and calling on Lebanon to control its territory, states in effect recognized that defensive force in foreign territory against NSAs is sometimes necessary given the host state’s inability (rather than its unwillingness) to prevent its territory from being used as a base of NSA operations. See further Armed Activities, Judgment, Separate Opinion of Judge Kooijmans, paras 27–31.

(78) See Trapp, State Responsibility for International Terrorism, 61.

(79) See Trapp, State Responsibility for International Terrorism, section 3.1.

(80) See Gray, International Law and the Use of Armed Force, 119.