The thesis examines the international law pertaining to the use of force by states, in general, and to the use of force in self-defence, in particular. The main question addressed is whether the use of force, which was purported to be in self-defence, by the United States, the United Kingdom and their allies against al Qaeda, the Taliban and Afghanistan, beginning on 7 October 2001, was lawful.
The thesis focuses not only on this specific use of force, but also on the changing nature of conflict, the definition of terrorism and on the historical evolution of limitations on the use of force, from antiquity until 2006. In the six chapters which trace the epochs of international law, the progression of five inter-related concepts is followed: limitations on the resort to force generally, the use of force in self-defence, pre-emptive self-defence, the use of forcible measures short of war, and the use of force in response to non-state actors.
This historical analysis includes a particular emphasis on understanding the meaning of the 'inherent right of self-defence', which was preserved by Article 51 of the United Nations' Charter. This analysis is then applied to the use of force against Afghanistan which occurred in 2001. Following the terrorist attacks of 11 September, the US and the UK notified the United Nations Security Council of their resort to force in self-defence under Article 51. Each element of Article 51 is analysed and the thesis concludes that there are significant doubts as to the lawfulness of that decision to employ force. In addition to the self-defence justification, other possible grounds for intervention are also examined, such as humanitarian intervention, Security Council authorisation and intervention by invitation.
This thesis challenges the common assumption that the use of force against Afghanistan was an example of states exercising their inherent right to self-defence. It argues that if this particular use of force is not challenged, it will lead to an expansion of the right of self-defence which will hinder rather than enhance international peace and security. Finally, this thesis draws on recent examples to illustrate the point that the use of force against Afghanistan could become a dangerous precedent for the use of force in self-defence.
