Use of force

Use of force is a politically sensitive and legally undetermined topic. It is therefore not surprising that it constitutes a highly controversial issue. During the Cold War, various critical debates about the legality of military interventions (Korea, Vietnam, Nicaragua, Palestine, Afghanistan) were prevalent. These controversies did not disappear in the 1990s (Yugoslavia) nor in the 2000s (Afghanistan, Iraq, Israel/Lebanon, Russia/Georgia, among others). A general assessment of the numerous books and articles dedicated to this issue reveals a deep ambivalence. On the one hand, no one really contests that the use of force is strictly forbidden in contemporary international law. This prohibition is recognized as a core rule of the law of nations, and even a rule of imperative international law (jus cogens). Indeed, it seems difficult to conceive any kind of legal order without at least affirming that its subjects cannot attack one another. The prohibition of the use of force is also logically linked to the notion of external sovereignty, aiming both at protecting the identity and the personality of every state and at preserving individuals “from the scourge of war” (preamble of the UN Charter). On the other hand, there are, to say the least, a great variety of interpretations of the rule. Are collective security and self-defense the only exceptions in allowing states to use force? Is the Security Council the only authority able to authorize states to use force? Under what conditions are states able to invoke self-defense? Those questions seem difficult to address, as the conventional sources are rather limited: Article 2(4) and Chapters VII and VIII of the UN Charter are far from providing explicit answers to all the questions raised. Thus, the answers can be found mainly in customary international law, with all the difficulties surrounding the task of establishing that law.