The Chatham House Principles of International Law on the Use of Force in Self-Defence

There are few more controversial questions in international law than the proper limits of the right of self-defence. The rules are being challenged in the light of what are seen as new threats from terrorism and from the possession of weapons of mass destruction. The UN High-level Panel, in its report to the Secretary-General of 2004, concluded that in all cases relating to decisions to use military force ‘we believe that the Charter of the United Nations, properly understood and applied, is equal to the task’.4 The Principles that follow are intended to provide a clear statement of the rules of international law ‘properly understood’ governing the use of force by states in self-defence.