The Threat of Force as an Action in Self-Defense under International Law

Green, James A., Grimal, Francis, Vanderbilt Journal of Transnational Law

ABSTRACT

Self-defense is a universally accepted exception to the prohibition of the use of force in international law, and it has been subjected to careful academic scrutiny. The prohibition of the threat of force, although equally important in terms of its normative status to the prohibition on use, has attracted far less academic commentary to date. This Article examines the relationship between the two prohibitions--of the use and threat of force--and considers the largely unexplored possibility of states utilizing a threat of force as a means of lawful defensive response: self-defense in the form of a threat. The status of this concept under international law is assessed, and the criteria that may regulate it are analyzed. This Article is based on an analogy between traditional "forcible" self-defense and the notion of threats made in self-defense. However, one cannot automatically apply the well-established rules of self-defense to a defensive threat, largely because of the practical differences between a threatened response and a response involving actual force.

TABLE OF CONTENTS
  I. INTRODUCTION
 II. THE THREAT OF FORCE IN INTERNATIONAL LAW
     A. The Source of the Prohibition of the
        Threat of Force
     B. The Jurisprudence of the ICJ and the
        "Coupling" of Use and Threat
     C. Typology of Threats of Force
III. SELF-DEFENSE INVOLVING THE USE OF FORCE
     A. "Traditional" Self-Defense: The Use of
        Force in Response to the Use of Force
     B. Anticipatory and Preemptive Self-Defense:

        The Use of Force in Response to the
        Threat of Force
 IV. IS NON-FORCIBLE SELF-DEFENSE
     CONCEPTUALLY POSSIBLE?
  V. IS THE THREAT OF FORCE IN SELF-DEFENSE
     DESIRABLE?
 VI. THE CRITERIA FOR SELF-DEFENSE INVOLVING
     THE THREAT OF FORCE
     A. In Response to What?
     B. Necessity and Proportionality
     C. Note on Collective Self-Defense
VII. CONCLUSION

A bully is not reasonable.

He is persuaded only by threats.

--Marie de France, late twelfth century

I. INTRODUCTION

The prohibition of the threat of force stands directly alongside its loftier counterpart, the prohibition of the use of force, in Article 2(4) of the United Nations Charter. (1) Yet, although states continually reference the prohibition of the use of military force (even while breaking it), the scope and nature of the prohibition of the threat of force has found little articulation in state practice. This discrepancy is also apparent in the writings of scholars. As such, numerous questions remain unanswered with regard to the status of threats of force in international law. This Article considers one such issue: the relationship between the prohibition of the threat of force and the international law governing self-defense.

In contrast to the legal status of threats of force generally, the lawfulness of forcible self-defense taken in response to a threat of force has been exhaustively, and exhaustingly, discussed in the academic literature. This debate over the lawfulness of "anticipatory" and "preemptive" self-defense has raged all the more fiercely since the atrocities of September 11, 2001, and the subsequent "war on terror." (2) However, the literature has left the inverted question, whether self-defense can be manifested by way of a threat of force, almost entirely unasked. (3) Therefore, it is not our intention to examine the question of whether military force taken in self-defense may be lawful in response to a threat. Instead, we ask whether a threat of force (a prima facie unlawful action under Article 2(4) (4)) can gain the status of lawfulness if taken as a defensive response, and, assuming that it can, we ask what criteria may be used to determine the lawfulness of such a defensive threat. This Article thus examines the legality of threats made in self-defense, which may also be referred to as "countervailing threats." (5)

In 1996, as discussed in Part II, the International Court of Justice (ICJ) concluded that a threat of force is unlawful when the force threatened would itself be unlawful, and that, correspondingly, the threat to use force in a lawful manner is itself lawful. (6) If this conclusion is accepted, "not only is every threat illegal where force is illegal, but, obviously, any justification put forward for the use of force will work equally well for the threat of such force." (7) Self-defense is a universally accepted exception, enshrined in both Article 51 of the UN Charter and in customary international law, to the general prohibition of the use of force. (8) Therefore, countervailing threats of force may be lawful if the threatened force meets the criteria regulating the actual use of force in self-defense.

Although a handful of other writers have also reached this conclusion, (9) none have taken the obvious next step and considered the criteria by which such a concept would be assessed. This Article aims to take that step, based on the core premise that defensive threats should be viewed as broadly analogous to "traditional" self-defense through the use of force. Having said this, it is not simply the case that the rules for the use of force in self-defense can be directly transposed to instances where a threat is employed. The use of force and the threat of force, while conceptually cut from the same legal cloth, are practically different actions with practically different consequences. (10) Therefore, the analogy to "traditional" self-defense is, on occasion, necessarily departed from or stretched.

This basic assumption is nonetheless an important starting point because there is little legal guidance beyond it as to the criteria required to turn an unlawful threat of force into a lawful one. As previously noted, there is only a very small amount of literature on the notion of threats made in self-defense. Moreover, states simply do not make the explicit legal claim that the wrongfulness of any given threat is precluded because that threat constituted an act of self-defense. Analysis of state practice provides little to indicate how customary international law treats threats in self-defense, because states do not tend to respond to this issue in legal terms: "Practice does not seem sufficiently unambiguous to make unfailingly intelligible distinctions among genuine approval of acts of self-help, reluctant acquiescence in them and resigned recognition of a fait accompli." (11) Therefore, the discussion that follows is necessarily speculative and, indeed, somewhat tentative. (12)

Nevertheless, states certainly do make threats, in a manner analogous to a use of force in self-defense, in response to a prior use (or threat) of force against them. (13) The question, then, is whether such threats should be considered lawful and, if so, on what basis. In tackling that question, it is important to note that this Article does not propose a reform of the current legal regime. Instead, it examines whether the existing framework already provides for the lawfulness of threats of force in the context of a defensive response and how the regulation of such actions should be explicitly assessed.

Part II briefly sets out the nature and scope of the prohibition of the threat of force in international law and its relationship to the prohibition of the use of force. Part III outlines the key traditional criteria for self-defense. Part IV examines whether the notions of non-forcible self-defense, generally, and self-defense by way of a threat, specifically, are even conceptually possible. It concludes that there is nothing to preclude states from manifesting self-defense in this way and, moreover, that countervailing threats are a logical aspect of the existing system. Part V argues that the threat of force in self-defense is not only conceptually possible under the current law, but that it is a desirable feature of it. Finally, Part VI examines how such a manifestation of the right of self-defense may be regulated, based on the existing criteria for self-defense as commonly understood.

II. THE THREAT OF FORCE IN INTERNATIONAL LAW

The absolute prohibition against the inter-state threat of force is contained in the first limb of Article 2(4) of the UN Charter. It Unfortunately, Article 2(4) itself offers little concrete guidance as to what conduct triggers a breach of the prohibition of the threat of force. Indeed, the Charter remains silent as to how international law defines (or should define) a threat of force. This deficiency has led to academic debate as to what a threat of force actually entails and at what point a "threat" violates Article 2(4). (15) To constitute a breach of the prohibition, must a threat of force be delivered as a classic verbal ultimatum--"comply or else"? Can nonverbal actions, such as conducting military exercises, also constitute threats of force in prima facie violation of the prohibition? This second question is particularly relevant to the relationship between threats and self-defense: a state may nonverbally communicate a defensive threat, for example, by positioning troops on its borders. (16)

This Part briefly sets out general understandings of the threat of force as regulated by international law. It first considers the legal source of the prohibition of the threat of force, through reference to the UN Charter and other quasi-statutory material. It then considers the extent to which the ICJ has examined the threat of force and highlights how the Court has conceptually "coupled" threats with the use of force. Finally, this Part sets out a typology of threats to use force that states may make in international relations.

A. The Source of the Prohibition of the Threat of Force

Like the prohibition of the use of force, the prohibition of the threat of force is binding on all members of the United Nations because it is explicitly provided for in Article 2(4) of the UN Charter: "All Members shall refrain in their international relations from the threat or use of force against the territorial integrity or political independence of any state, or in any other manner inconsistent with the Purposes of the United Nations." (17)

The prohibition of the threat of force has also been restated, albeit in a soft law format, in subsequent international instruments, such as the 1970 Declaration on the Principles of International Law Concerning Friendly Relations and Cooperation Among States (18) and the 1987 Declaration on the Enhancement of the Effectiveness of the Principle of Refraining from the Threat or Use of Force in International Relations. (19)

However, neither of these soft law instruments goes beyond a restatement of Article 2(4). The 1970 Declaration sets out that every state "has the duty to refrain in its international relations from the threat or use of force against the territorial integrity or political independence of any State, or in any manner inconsistent with the purposes of the United Nations." (20) It proceeds to confirm that "[s]uch a threat or use of force constitutes a violation of international law and the Charter of the United Nations and shall never be employed as a means of settling international issues." (21) Similarly, the 1987 Declaration provides that "[e]very State has the duty to refrain in its international relations from the threat or use of force against the territorial integrity or political independence of any State, or in any other manner inconsistent with the purposes of the United Nations." (22) At this juncture, it is enough to note that neither Article 2(4) of the UN Charter nor the declarations that reinforce the prohibition give any obvious guidance as to when a threat of force is unlawful or under what circumstances it would be permissible. (23)

B. The Jurisprudence of the ICJ and the "Coupling" of Use and Threat

It is therefore useful to turn to the jurisprudence of the ICJ for guidance as to the nature and scope of threats of force. However, only a few ICJ decisions even refer to threats of force, let alone discuss them in detail or provide any substantial guidance in terms of defining the lawfulness of a threat of force. Of the decisions that do refer to threats of force, the Court's analysis is generally rather superficial. As these decisions are well documented, our factual discussion is kept to a minimum. This subpart, therefore, primarily concentrates on distilling the ICJ's position in its 1996 advisory opinion on the Legality of the Threat or Use of Nuclear Weapons, (24) which is crucial for our subsequent analysis.

The first case to consider threats of force in international law, though, was the Corfu Channel merits decision of 1949, which arose from the destruction of two British destroyers by mines off the Albanian coast. (25) In response to the United Kingdom's application to the ICJ, Albania asserted that British warships in the Corfu Straits had twice violated Albanian sovereignty in breach of international law. (26) First, Albania alleged that the threatening nature of the tactical "diamond formation" adopted by the British destroyers and other supporting vessels, prior to the two destroyers striking Albanian mines, was a breach of its sovereignty. (27) With regard to this claim, the ICJ took the view, in light of the circumstances, that the British action was threatening but nonetheless lawful. (28)

The second incident alleged as a breach of sovereignty by Albania was known as Operation Retail. This operation involved the sweeping for and removal of mines in the Corfu Straits by the Royal Navy following the initial sinking of the British destroyers. (29) The ICJ viewed this incident "as the manifestation of a policy of force... [that cannot] find a place in international law." (30) However, the Court went on to state that it did not see this action as "an unnecessarily large display of force" and therefore did "not consider that the action of the British Navy was a demonstration of force for the purpose of exercising political pressure on Albania." (31) As a result, the Court found the minesweeping action to be an unlawful breach of Albanian sovereignty because it was a use of force. (32) Rather confusingly, though, the Court implied that this use of force was not itself threatening, or, at least, that it was not intended to be threatening. (33) This aspect of the Corfu Channel judgment could be interpreted as indicating that the prohibition of the use of force was breached, but that the prohibition of the threat of force was not. Of course, this interpretation is speculative because the Court did not phrase its findings in these terms; indeed, it did not refer directly to Article 2(4) or its prohibitions at all.

Part IV returns to the Corfu Channel decision, but for present purposes, it is enough to note that the Court was not especially explicit in its examination of threats of force. The judgment may cause more confusion than clarity on the issue. Nonetheless, what is clear is that the ICJ indicated--albeit rather equivocally--that not all threatening behavior is necessarily a breach of Article 2(4). Corfu Channel, therefore, underlines the difficulty of determining whether any given action constitutes an unlawful threat of force, but it does little to resolve that difficulty.

In Nicaragua v. United States, a 1986 case concerning support of the Contra guerillas by the United States, the first reference to the threat of force occurs in paragraph 195 of the judgment, where the Court defined the concept of an "armed attack." (34) According to the Court, an "armed attack" does not include "assistance to rebels in the form of the provision of weapons or logistical or other support." (35) Instead, the Court deemed such "assistance" to be a "threat or use of force, or ... intervention in the internal or external affairs of other States." (36) It is unlikely that either the provision of weapons or other forms of logistical support involve the actual use of force. For example, if state A supplies machine guns to a paramilitary organization for use against state B, there has been no use of force by state A against state B, even indirectly. However, this action is clearly a threat: supplying the paramilitary organization with weaponry indirectly threatens state B. Therefore, this aspect of the Nicaragua judgment does little more than indicate one possible manifestation of an unlawful threat of force.

The Court's most important decision regarding the status of threats in international law is the Nuclear Weapons advisory opinion of 1996, in which it considered whether the threat or use of nuclear weapons was "permitted" under international law. (37) The ICJ recognized that "states sometimes signal that they possess certain weapons to use in self-defence against any state violating their territorial integrity or political independence." (38) One issue before the Court, therefore, was whether such a "signalled intention" constituted a threat within the ambit of Article 2(4):

   Whether a signalled intention to use force if certain events occur
   is or is not a "threat" within Article 2, paragraph 4, of the
   Charter depends upon various factors. If the envisaged use of force
   is itself unlawful, the stated readiness to use it would be a
   threat prohibited under Article 2, paragraph 4.... [equally] if it
   is to be lawful, the declared readiness of a State to use force
   must be a use of force that is in conformity with the Charter. (39)

This statement clearly establishes that a threat to use force can constitute a lawful action, and, moreover, that the lawfulness of any threat of force is contingent upon the prospective lawfulness of the force threatened. The Court's 1996 finding is the most authoritative statement of this position, but it was far from novel. Indeed, the Court briefly noted in the 1986 Nicaragua case that the threat of force "is equally forbidden by the principle of non-use of force." (40) Although this statement seems somewhat nonsensical--it would seem illogical for the prohibition of use to also prohibit threats because use and threat are different things--it can reasonably be interpreted to mean that the Court viewed the threat of force as being "equally forbidden" by Article 2(4), or that the threat of force and the use of force are "equally forbidden."

The conceptual "coupling" of the prohibitions of threat and use of force, to the extent that lawful force can be lawfully threatened and vice versa, has also long since been the majority position taken in the (admittedly limited) academic commentary on threats in international law. For example, in 1963, Ian Brownlie stated that "[i]f the promise is to resort to force in conditions in which no justification for the use of force exists, the threat is itself illegal." (41) More recent literature reaffirms this position, (42) although some scholars admittedly take an alternative view. (43)

Ultimately, despite the lack of clarity in the international instruments prohibiting the threat of force and the ambiguity of state practice on this issue, it seems evident, from both the Nuclear Weapons opinion and the wider literature, that if actual force is unlawful, then, retroactively, so is the threat to use that same force. (44) Similarly, lawful force can be lawfully threatened. (45) Article 2(4) is a binding normative provision prohibiting the threat or use of force, and the only universally accepted means of lawfully justifying the use of force are under Articles 42 and 51 of the Charter. (46) Thus, we argue that the same proposition must apply for threats. All threats of force are prima facie unlawful. (47) A threat is therefore permissible only if the actual force threatened is permissible--meaning that it falls under Article 42 or 51. (48)

C. Typology of Threats of Force

At this juncture, it is useful to briefly identify several categories of threats that are apparent in state practice. Given that Article 2(4) and other international instruments are essentially silent on the issue and the ICJ has provided only minimal guidance, this subpart provides a brief typology of actions that potentially violate the prohibition of the threat of force.

The fact that Article 2(4) fails to define a threat of force has led legal commentators to attempt to clarify the concept. Romana Sadurska, for example, defined a threat of force as "a message, explicit or …

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Publication information: Article title: The Threat of Force as an Action in Self-Defense under International Law. Contributors: Green, James A. - Author, Grimal, Francis - Author. Journal title: Vanderbilt Journal of Transnational Law. Volume: 44. Issue: 2 Publication date: March 2011. Page number: 285+. © 1999 Vanderbilt University, School of Law. COPYRIGHT 2011 Gale Group.

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