This text explores the large and controversial subject of the use of force in international law, including use of force by States, the role of the UN, and the role of regional organizations in the maintenance of international peace and security.

This book explores the large and controversial subject of the use of force in international law. It examines not only the use of force by states but also the role of the UN in peacekeeping and enforcement action, and the increasing role of regional organizations in the maintenance of international peace and security. The UN Charter framework is under challenge. Russia's invasion of Georgia and intervention in Ukraine, the USA's military operations in Syria, and Saudi Arabia's campaign to restore the government of Yemen by force all raise questions about the law on intervention. The 'war on terror' that began after the 9/11 terrorist attacks on the USA has not been won. It has spread far beyond Afghanistan: it has led to targeted killings in Pakistan, Somalia, and Yemen, and to intervention against ISIS in Iraq and Syria. Is there an expanding right of self-defence against non-state actors? Is the use of force effective? The development of nuclear weapons by North Korea has reignited discussion about the legality of pre-emptive self-defence. The NATO-led operation in Libya increased hopes for the implementation of 'responsibility to protect', but it also provoked criticism for exceeding the Security Council's authorization of force because its outcome was regime change. UN peacekeeping faces new challenges, especially with regard to the protection of civilians, and UN forces have been given revolutionary mandates in several African states. But the 2015 report Uniting Our Strengths reaffirmed that UN peacekeeping is not suited to counter-terrorism or enforcement operations; the UN should turn to regional organizations such as the African Union as first responders in situations of ongoing armed conflict.

1. Law and Force; 2. The Prohibition of the Use of Force; 3. Invitation and Intervention: Civil Wars and the Use of Force; 4. Self-defence; 5. Collective Self-defence; 6. The Use of Force against Terrorism: a New War for a New Century; 7. The UN and the Use of Force; 8.

When the United Nations Charter was adopted in 1945, states established a legal `paradigm' for regulating the recourse to armed force. In the years since then, however, significant developments have challenged the paradigm's validity, causing a `pardigmatic shift'. International Law and the Use of Force traces this shift and explores its implications for contemporary international law and practice.

The international law on the use of force is one of the oldest branches of international law. It is an area twinned with the emergence of international law as a concept in itself, and which sees law and politics collide. The number of armed conflicts is equal only to the number of methodological approaches used to describe them. Many violent encounters are well known. The Kosovo Crisis in 1999 and the US-led invasion of Iraq in 2003 spring easily to the minds of most scholars and academics, and gain extensive coverage in this text. Other conflicts, including the Belgian operation in Stanleyville, and the Ethiopian Intervention in Somalia, are often overlooked to our peril. Ruys and Corten's expert-written text compares over sixty different instances of the use of cross border force since the adoption of the UN Charter in 1945, from all out warfare to hostile encounters between individual units, targeted killings, and hostage rescue operations, to ask a complex question. How much authority does the power of precedent really have in the law of the use of force?

The nations that drafted the UN Charter in 1945 clearly were more concerned about peace than about justice. As a result, the Charter prohibits all use of force by states except in the event of an armed attack or when authorised by the Security Council. This arrangement has only very imperfectly withstood the test of time and changing world conditions. In requiring states not to use force in self-defence until after they had become the object of an actual armed attack, the Charter failed to address a growing phenomenon of clandestine subversion and of instantaneous nuclear threats. Fortunately although the Charter is very hard to amend, the drafters did agree that it should be interpreted flexibly by the United Nations' principal political institutions. In this way the norms governing use of force in international affairs have been adapted to meet changing circumstances and new challenges. The book also relates these changes in law and practice to changing public values pertaining to the balance between maintaining peace and promoting justice.