Public international law is the system of laws that govern the relationship between states and other players in international law. Such law is working well at a low level—for example, the use of passports to travel between states. At a higher level, however, Art 2(4) of the United Nations Charter (and customary international law) is not being complied with. Article 2(4) forbids the threat or use of force against states in any manner inconsistent with the purposes of the UN Charter, which are to maintain world peace and security. The right of self-defence exists under Art 51 of the UN Charter, which refers to ‘the inherent right of individual or collective self-defence if an armed attack occurs’ until the UN Security Council has acted. Pre-emptive strikes by states that reasonably believe an attack upon them is imminent are permissible under international law, provided the criteria of necessity and proportionality are present. Thus, the use of force must meet the demands of necessity and proportionality.
