Note: The content of this post maybe outdated.
A State can rely on its inherent right of self defense when it is (1) necessary: that is to say that the threat or use of force is instant, overwhelming, leaving no alternatives and no moment of deliberation; and (2) proportionate: the force used in self defense is proportionate to the threat or use of force. (This position was formulated after the Caroline Incident that took place in 1837 when the British sank a ship with insurgents in American territory and after British citizen was charged for sinking the ship.)
Under customary law a State use self defense:
- When an armed attack occurred: see our discussion on the Israel/ Lebanon/ Hezbollah conflict in 2006.
- In anticipation of an armed attack or threat to State security: consider what we learnt on the recent US attack on Iraq based on the alleged existence of nuclear weapons (WMD). This was justified by US as “anticipatory SD” (this is also called “preemptory self defense”.) ✐ Is anticipatory SD liable to be abused?
- In response to an attack or threat of attack against State interests (nationals and property of the State). See our discussion on the Entabbe incident, where Israel justified the use of force in Ugandan territory against the PLO as SD. US invasions in Panama and Grenada were also justified on the basis of protecting US nationals in those countries.
- where the “attack” doesn’t involve the use of force and involves, instead, economic aggression that is instant and overwhelming.