The United Nations, states and regional organisations have spent invaluable time and resources to maintain international peace and security in a largely anarchical international system, owing to armed conflicts between states and non-state actors (NSAs). This state of affairs is exacerbated by the proliferation of weapons of mass destruction, transnational terrorist networks, failed states and a disregard for international norms by powerful states. This is in spite of the normative and policy frameworks that have been established to constrain the use of force by states in the territories of one another. Article 2(4) of the United Nations Charter prohibits the use of force by states in their relations, unless they rely on the exceptions in articles 51 and 42 and the customary law doctrine of ?consent?. In addition, it was the requirement of international law that a state may use force against NSAs, only if it attributes the conduct of the NSAs to a state. This thesis examines the extraterritorial use of force by states against terrorist non-state actors, and the focus is to answer the question ?whether the law of self-defence has been transformed?. The investigation has been conducted with particular attention to whether the post 9/11 practice of states, the Security Council resolutions 1368 and 1373, the use of pre-emptive self-defence by the United States, Israel and a few other states, the disregard for attribution of the conduct of NSAs to states and the overwhelming international support for contemporary incidents of the use of force by states against NSAs, such as Al Qaeda, the Taliban, Al-Shaabab, the Khorasan Group and the Islamic State of Iraq and the Levant, have caused a change in the law of self-defence.
Firstly, the study finds that pre-emptive self-defence which does not require imminence has not been accepted as part of international law and it argues that its unlawful use could not cause a change in the law. Secondly, as far as the use of self-defence against non-state actors is concerned, it finds that the actions of the United States against Al Qaeda following resolutions 1368 and 1373 of the Security Council, the lowering of the attribution standard and the toleration by the international community of the use of force against terrorists in Afghanistan, Iraq, Syria, Lebanon, Yemen, Pakistan, Ecuador, Somalia and Mali without attributing their conduct to states, could be interpreted as amounting to a transformation of the law of self-defence.
Accordingly, this study recommends the acceptance of the lowered threshold in the attribution requirement, but it also recommends a corresponding disregard of ?pre-emptive self-defence? as not forming part of the corpus of international law. It is also recommended that the jurisdiction of the International Criminal Court be enlarged to try transnational terrorism as one of the egregious crimes against mankind.