Jus ad bellum and jus in bello are not disparate in operation. There are several points of intersection in the two concepts, commencing with the context in which they apply, and further, in their interpretation of the general principles of proportionality and necessity. Although proportionality connotes divergent theoretical notions depending on the backdrop against which it is set, in practice, these notions are often fused together. However, points of fission (divergence) still persist. The best example of which is in the context of 'The Crime of Disproportionate Use of Force' where the difference between the two notions of 'proportionality' can be described as the limitations on the overall force used to respond to an armed attack under jus ad bellum as opposed to the balance between the anticipated military advantage weighed against the resulting loss of civilian life under jus in bello. The authors argue that there is need for fusion (convergence) between jus ad bellum and jus in bello particularly in relation to modern war crimes trials in order to ensure that both principles have practical significance. This would ensure further convergence between jus in bello and jus ad bellum. To fulfill the shielding purpose of law in the context of armed conflict, more fusion between these two concepts must be embraced in all fora, including, conceptualization of crime of aggression and distinguishing between combatants and civilians.
CONTENTS I. INTRODUCTION A. Unlawful Use of Force: Assessing Jus Ad Bellum 1. Introduction 2. Unlawful use of force in jus ad bellum: The Case of Disproportionate Use of Force 3. Unlawful use of force in jus in bello: The Case of Disproportionate Use of Force 4. Conclusion B. Points of Fusion: Proportionality Under jus in bello and jus ad bellum 1. Introduction 2. The Fission: The Crime of Disproportionate Use of Force Not Justified By Military Necessity C. Constructing a Fusion: The Crime of Disproportionate Use of Force not justified by Military Necessity 1. Conceptualizing the Crime of Aggression 2. Unlawful Use of Force as a War Crime 3. Constructing a Fusion: Jus ad Bellum and Jus in Bello in relation to Combatants and Civilians 4. Distinguishing Combatants from Non-Combatants 5. Combatants' in bello and ad bellum responsibility II. CONCLUSION I. INTRODUCTION
The cardinal principle governing jus in bello demands a distinction between combatants and civilians and authorizes the attack of the former. In essence, loss of civilian life is prohibited unless it occurs within the context of the principles of necessity and proportionality. In contrast, the cardinal principle governing jus ad bellum is that States are not allowed to use force unless done in individual or collective self-defense. Based on the foregoing, then, two questions arise. First, can the use of force in wars of aggression be prosecuted as the war crime of disproportionate force not justified by military necessity? Second, do the principles of proportionality and necessity play an extended role where jus ad bellum has been observed, hence creating a wider justification to an eventuality of loss of civilian life or negating lawful use of force to unlawful use not justified by any military necessity?
Prior to the development of modern international law and the advent of the League of Nations and the United Nations, the legal rules that governed the use of force by nations were derived solely from the norms of customary international law. These were norms that would arise from the convergence of general and consistent State practice and opinio juris. (1) Early attempts at developing a concrete and binding legal statement on the prohibition of the use of armed force through multilateral treaties such as the Covenant of the League of Nations, (2) and the Kellogg-Briand Pact (3) proved ineffective and were ultimately replaced by the United Nations Charter.
In this regard, the authors posit that there is need for fusion (convergence) between jus ad bellum and jus in hello particularly in relation to modern war crimes trials in order to ensure that both principles have practical significance. The principles of proportionality and necessity as used in jus ad bellum and as used in jus in hello can be fused for practical significance and to bolster the position of jus ad bellum and jus in hello in enforcement of international criminal law. The authors argue that in the assessment of proportionality and necessity under jus in hello, international tribunals can, and have in the past, considered proportionality and necessity in jus ad bellum. This makes the case for the fusion of the concepts in the unlawful use of force vis-a-vis the war crime disproportionate use of force, not justified by military necessity.
For easier comprehension, the authors have divided the essay into three broad parts: Part I assesses jus ad bellum in a generic sense and its relationship to the cases of disproportionate use of force as viewed from a jus ad bellum point of view. Part II then addresses the points of fission (divergence) and fusion (convergence) between jus ad bellum and jus in bello. Here the authors do not attempt any arguments on whether there should be any kind of fission or fusion between the two
broad parts. Part III then endeavors to argue for the construction of more fission between the two areas of law using the war crime of disproportionate use of force not justified by military necessity as a backdrop. The last part in this section seeks to draw a case for more fusion by using the dichotomy of combatants and civilians in jus in hello and jus ad helium as a focus area. In this part the authors argue for a convergence of the two broad concepts of international law for morally justifiable outcomes. This is done with the background understanding that the two concepts are currently viewed as divergent when it comes to enforcement under international criminal law.
Unlawful Use of Force: Assessing Jus Ad Bellum
While the most common starting point in the assessment of the modern unlawful use of force is the United Nations Charter, the idea of a "just war" is in essence a transformation of older ideas.
Two Catholic saints, Augustine and Thomas Aquinas are credited with formulation of a "just war" doctrine. (4) This doctrine is characterized by three main principles: the authoritativeness of the initiator of war, just reasons for waging war, and the legitimate intentions of war. (5) Due to obvious ties of the foregoing writers to the Church, this viewpoint was characteristically founded on natural law. (6)
Although this doctrine has been expanded numerously in subsequent years, the cardinal principles have been maintained, as evidenced by the relevant provisions in the United Nations Charter. (7)
Article 2(4) of the Charter contains the general proscription against the use of force: "[a]ll Members shall refrain in their international relations from the threat or use of force against the territorial sovereignty or political independence of any state, or in any other manner inconsistent with the Purposes of the United Nations. (8)" This provision is couched in mandatory terms, exposing the seriousness in which the concept of jus ad bellum is regarded.
However, Article 51 of the UN Charter then contains a limited exception to the general prohibition on the use of force:
Nothing in the present Charter shall impair the inherent right of individual or collective self-defence if an armed attack occurs against a Member of the United Nations, until the Security Council has taken measures necessary to maintain international peace and security. Measures taken by Members in the exercise of this right of self-defence shall be immediately reported to the Security Council and shall not in any way affect the authority and responsibility of the Security Council under the present Charter to take at any time such action as it deems necessary in order to maintain or restore international peace and security ... (9) This article, therefore, provides for the permissible cases when a State may use armed force, that is, in situations of individual or collective self-defense. However, there is a caveat attached: there must be a United Nations Security Council Resolution supporting this action. Thus, the assumption here is that when a State takes up arms against another State or entity, said State or entity will be acting in violation of the rule prohibiting the resort to force in international law embedded in Article 2(4) of the UN Charter. This serious violation found in Article 2(4) is termed aggression. (10) The entity who violates this provision against a State would therefore be an aggressor under international law. For purposes of this article, the party that is subject to the aggression will be referred to as the "self-defending State or entity."
Therefore, what is referred to as unlawful use of force is really the violation of Article 2(4) of the UN Charter. If States or non-State entities resort to use of force other than as authorized under the UN Charter, that use of force is unlawful under international law. This means that while the general rule seems to be founded on the prohibition of the use of force, the use of force in international relations is not unlawful, except as authorized by the United Nations Charter. Despite this sense of general prohibition on the resort to the use of force in the UN Charter, conflict and hostilities that involve the use of armed force remain constant features of the international politics. (11)
From this general principle on jus ad bellum four legal consequences come to bear. The first being that what was previously a legal status of a "declaration of war" (12) no longer exists. States can no longer avail themselves to what was previously known as "belligerent rights." These rights include "the seizure of enemy ship or other property at sea or on land under the law of naval warfare...