The Permissibility of Unilateral Intervention under International Law

Article excerpt


The invasion of Iraq by the United States led allied forces in April 2003 without explicit authorisation of the United Nations Security Council raised many questions about the legal basis of unilateral armed intervention. This article considers rules based on the Charter of the United Nations pertaining to intervention and poses the question whether existing rules of international law are adequate to contain international conflict and uphold peace and security. Recent examples of state practice of unilateral armed intervention appear to be in violation of international law. Since state practice presents an important formative force of rules of international law, existing rules regulating armed intervention are under increased pressure due to their restrictive nature. The question is examined whether or not the phenomenon of unilateral intervention points to the development of new rules of international law. Alternative options are suggested on how to address unilateral intervention within the confines of international law.


The invasion of Iraq by armed forces of the United States (US), the United Kingdom (UK) and Australia during April 2003 led to mixed reaction from the world's international law community. Reactions ranged from outright condemnation of the war as unlawful to careful attempts to identify a legal basis for unilateral armed intervention. This difference of opinion calls for an assessment of the rules of international law. A lack of legitimacy of existing rules amongst the most important role players in world politics may point to a need for reassessment.

The international political landscape has undergone dramatic and irreversible changes since the end of the Cold War which include the fragmentation of the former Soviet Union; the emergence of the US as the world's only superpower; rapid globalisation; and an increase in large-scale terrorist attacks epitomised by the September 11, 2001 attack on the US. The achievement of world peace and security in a post-Cold War world presents challenges which were not foreseen when the United Nations (UN) was established after the Second.World War. (1)) The war in Iraq is the most recent in a series of events questioning the sufficiency of the existing rules of international law particularly those embodied in the Charter of the United Nations, designed to maintain peace and security in a changed world.

The recurring inability of the UN to react speedily to resolve international conflicts has resulted in intervention by the US and other major powers to deal with such events without prior approval of the UN. Such intervention can be labelled unilateral intervention. International reaction to unilateral intervention has varied from case to case. On the one hand, many states have reacted favourably to unilateral intervention where the UN retained some form of involvement in resolving the relevant international disputes even if it manifested in ex post facto approval by the Security Council. The ex post facto legalisation of the North Atlantic Treaty Organisation's (NATO) military intervention in Yugoslavia by the UN serves as an example. On the other hand, there has been mixed reaction where the US has acted or sought to act outside the UN framework. One such example is the military intervention in Afghanistan. Although the world was unanimous in its condemnation of the terrorist attacks on the US by al-Qaeda on 11 September 2001, the legality of the US armed attacks in Afghanistan were questioned in the face of international law principles. (2)) This was especially the case in so far as the military intervention was geared towards removing the incumbent regime and replacing it with a government partisan to the US and its allies. (3))

Without doubt, recent actions by the US and other major powers have raised many issues in international law, which warrant an in-depth consideration. (4)) This article investigates the legality in terms of existing international law of recent unilateral actions by the US, its allies and NATO to preserve international peace and security. …