International law aims to regulate the use of force in two ways. First, it stipulates that there is a paramount obligation not to use force to settle disputes, with only limited exceptions; and second, it has at its disposal a procedure whereby the international community itself may use force against those using violence. These are known respectively as the rules on the ‘unilateral use of force’ and the rules of ‘collective security’, both of which are discussed in this chapter.
Chapter
15. The Use of Force, Collective Security and Peacekeeping
Chapter
20. The Use of Force and the International Legal Order
Christine Gray
This chapter examines the law on the use of force. It discusses the UN Charter scheme; the Prohibition of the Use of Force in Article 2(4) of the UN Charter; intervention, civil wars, and invitation; self-defence; the use of force under Chapter VII of the UN Charter; UN peacekeeping; and regional action under Chapter VIII of the UN Charter. The UN Charter provisions on the use of force by States, Article 2(4) on the prohibition of force, and Article 51 on self-defence, have all caused fundamental divisions between States. There is disagreement as to whether the prohibition on force should be interpreted strictly or whether it allows humanitarian intervention, as in Kosovo. There is also disagreement over the scope of the right of self-defence. The response to the 9/11 terrorist attacks has led to a fundamental reappraisal of the law in this area.
Chapter
11. Use of force
This chapter examines under what circumstances States may use armed force under customary international law and Arts 2(4) and 51 UN Charter. After noting that the use of armed force is generally prohibited and only limited to self-defence, and then only if the target State is under an armed attack, we show that several States have expanded the notion of armed attack. Besides self-defence, the United Nations Security Council may authorize the use of armed force through a process of collective security. Several examples of collective security are offered, as well as the ICJ’s position on what constitutes an armed attack. In recent years, the range of actors capable of undertaking an armed attack has included terrorists. Moreover, the development of the doctrine of the responsibility to protect is a significant achievement.
Chapter
20. The Use of Force and the International Legal Order
Christine Gray and Andrew Sanger
This chapter examines the law on the use of force. It discusses the UN Charter scheme; the Prohibition of the Use of Force in Article 2(4) of the UN Charter; intervention, civil wars, and invitation; self-defence; the use of force under Chapter VII of the UN Charter; UN peacekeeping; and regional action under Chapter VIII of the UN Charter. The UN Charter provisions on the use of force by States, Article 2(4) on the prohibition of force, and Article 51 on self-defence, have all caused fundamental divisions between States. There is disagreement as to whether the prohibition on force should be interpreted strictly or whether it allows humanitarian intervention, as in Kosovo. There is also disagreement over the scope of the right of self-defence. The response to the 9/11 terrorist attacks has led to a fundamental reappraisal of the law in this area.
Chapter
33. Use or threat of force by states
This chapter discusses international law governing the use or threat of force by states. The UN Security Council has primary responsibility for enforcement action to deal with breaches of the peace, threats to the peace, or acts of aggression. Individual member states have the right of individual or collective self-defence, but only ‘until the Security Council has taken measures necessary to maintain international peace and security’. However, the practice has evolved of authorizing peacekeeping operations that are contingent upon the consent of the state whose territory is the site of the operations.
Chapter
16. Collective Security and the use of Armed Force
Paola Gaeta, Jorge E. Viñuales, and Salvatore Zappalà
The Cold War era prevented the UN Security Council from using most of the powers provided for by the UN Charter, including adopting measures under Chapter VII (the so-called ‘collective security system’ which provides for measures ranging from sanctions to the use of armed force) for events deemed (by the Security Council) to be threats to the peace, breaches of the peace, or acts of aggression. However, the end of the Cold War enabled the Security Council to take some of the measures short of force envisaged in Article 41 and to interpret creatively the provisions of the Charter so as to authorize enforcement action through the use of armed force by individual States or coalitions of States. This chapter discusses measures short of armed force; peacekeeping operations; resort to force by States, as well as regional and other organizations, upon authorization of the Security Council; the special case of authorization to use force given by the General Assembly; as well as the right to self-defence and the various situations in which armed force has been used unilaterally by States.
Chapter
11. The Use of Force, Collective Security and Peacekeeping
International law aims to regulate the use of force in two ways. First, it stipulates that there is a paramount obligation not to use force to settle disputes, with only limited exceptions; and second, it has at its disposal a procedure whereby the international community itself may use force against those using violence. These are known respectively as the rules on the ‘unilateral use of force’ and the rules of ‘collective security’, both of which are discussed in this chapter. This chapter also explores individual criminal responsibility for the crime of aggression.
Chapter
12. Justifications and excuses
Antonio Cassese, Paola Gaeta, Laurel Baig, Mary Fan, Christopher Gosnell, and Alex Whiting
This chapter discusses the notions of justifications and excuse. Circumstances can sometimes arise that either justify criminal conduct, or excuse the perpetrator for engaging in it. A justification is a circumstance that makes the accused’s conduct preferable to even worse alternatives. Among the circumstances that negate unlawfulness of what would otherwise be a criminal act are: self-defence; necessity (as justification); and belligerent reprisals (for war crimes). An excuse, such as duress, involves an action that, while voluntary, nevertheless was produced by an impairment of a person’s autonomy to such a degree as to negate their blameworthiness. Mistakes of law, mental incapacity, or intoxication are also usually categorized as excuses, although strictly speaking, these are cognitive impairments that preclude the formation of a guilty mental state in the first place.
Chapter
14. The use of force and collective security
This chapter looks at the use of force and collective security. Today, the United Nations Charter embodies the indispensable principles of international law on the use of force. These include the prohibition on the unilateral use of force found in Article 2(4), and the recognition of the inherent right of all States to use force in self-defence found in Article 51. Finally, under Chapter VII, a collective security system centred upon the Security Council was established for the maintenance of international peace and security. A key debate over the scope of Article 2(4) is whether a new exception has been recognized which would allow the use of force motivated by humanitarian considerations. It is argued that these ‘humanitarian interventions’ would allow a State to use force to protect people in another State from gross and systematic human rights violations when the target State is unwilling or unable to act.
