The question of the legality and/or legitimacy of the use of force in international affairs has caused a debate within the transatlantic community, and therefore, within the United Nations as well. The author argues that the concept of ‘just war’, which has to originate both from a just cause and a just conduct, is shaken by the new threats, terrorism and weapons of mass destruction, that change the established rules : there are no more interstate conflicts but internal ones, no more proportional attacks and no more immunity for noncombatants. Faced with this situation of a new kind, the UN has attempted to set responses (peacekeeping, conflict prevention, duty of intervention), yet the UN has not defined a clear framework of the legality of the use of force. The author suggests eight points for thought and recommendation for the international and transatlantic community, in its search for legality for the use of force. – Summary AFRI-2005