This obligation, as it applies to the acts of a single nation, and the rather restrictive exceptions to it are known as the rules on unilateral use of force. At the same time, there is the concept of collective security, which allows the community of nations to arise and oppose an aggressor nation together. This is regulated by the rules of collective security. Therefore, there are many situations where disputes between nations can break down into open conflict, and such conflict may still be completely legitimate under international law.
'All Members shall refrain in their international relations from the threat or use of force against the territorial integrity or political independence of an State, or in any other manner inconsistent with the Purposes of the United Nations.'4
This builds on the preceding provision which places an obligation on Members to settle disputes peacefully5 which in turn follows from the very purposes and reasons for the United Nations, that being the maintenance of peace and security and the prevention and removal of threats thereto.6
De Arechega describes Article 2(4) as 'the cardinal rule of international law and the cornerstone of peaceful relations among States.'7 This altered the age-old rule, applying up till 1949, that use of force was a legitimate remedy of last resort in all international disputes. While the Covenant of the League of Nations and the Briand-Kellogg Treaty condemned the 'resort to war' this was interpreted as only covering an all out declaration of war, and not uses of force short of war, which became in practice, all out war so long as no declaration of such was made.
Article 2(4) therefore refers to 'force' and not 'war' and it expressly includes the threat of force. Force has been interpreted as armed force of all kinds, but not political pressure or economic sanction.
The wording of Article 2(4), although a marked improvement on predecessors, is still open to arguments as to interpretation. Probably the most obvious is the apparent qualification of the obligation only to cases where 'territorial integrity or political independence' is challenged. In the Corfu Channel Case (Albania v United Kingdom)8 the United Kingdom Navy entered Albanian waters to sweep mines. The ships did so and then left the Albanian waters. The United Kingdom argued that since its action threatened neither the territory nor independence of Albania, it did not breach 2(4). The International Court of Justice decided however that the action of the United Kingdom was an unlawful use of force.9 Article 2(4) can therefore, as far as it goes, be seen as a legal obligation on states to genuinely refrain from the use of force. However, despite its legal validity, it may not have been quite so successful in practice.
If Article 2(4) can be seen as a failure, I think the clearest demonstration of this is seen in the context of the Cold War. The Cold War attacked the resolve of 2(4) in two ways. The first was by changes in technology and the scope and effects that warfare would take on in the post nuclear