Terrorism and the Legality of Pre-emptive Force

The use of military force is only lawful if and to the extent that it comes under an accepted exception to the general rule prohibiting the use of force, i.e authorization by the Security Council and self-defence. Lawful self-defence requires the actual existence of an armed attack, or of a situation to be considered as equivalent to an armed attack. A threat may be so direct and overwhelming that one cannot require the victim to wait to act in self-defence until the attack has actually started. This principle of necessity and immediacy is still part of customary international law. The doctrine of pre-emptive strikes formulated in the recent US National Security Strategy proposes to adapt this concept to new perceived threats in a way that would constitute an unacceptable expansion of the right of anticipatory self-defence. Vagueness and the possibility of abuse of any broader definition requires maintaining the traditional strict approach. A change might result in the abolition of the prohibition of the use of force altogether. Opening up broader possibilities for anticipatory self-defence is not desirable. To face so-called new threats, recourse to the Security Council is preferable to unilateral use of force based on a doctrine of pre-emptive strikes.