In the second half of the last decade of the 20th century and beginning of the 21 st century, five important unilateral uses of force by some permanent members of the Security Council took place. In the most recent the outcome of the US and the UK incursion was the overthrow of Iraq’s Government, the occupation of Iraq by a foreign military force and the installation of a governor by the US Government as a temporary measure. In all cases, the intervening States tried to justify their action under the just war doctrine, pre-emptive self-defence, UN Charter and old SC resolutions. In this chapter, I will attempt to determine whether the decision by the US against Iraq in September 1996, the unilateral use of force against Iraq starting in December 1998 by the US and the UK, the threat and use of military force in March 1999 by NATO against Serbia over the Kosovo crisis, the US and UK unilateral action against Iraq in February 2001, and finally the war launched on 20 March 2003 against Iraq by the US and the UK without explicit SC authorisation, are justified under the common criteria of traditional Just War theory: just cause; competent authority; and right intention. 1 The final section of this chapter examines the doctrine of humanitarian intervention in international law and the tension between sovereignty and human rights as featured in the UN Charter. It also discusses some of the attempts of scholars who try to justify the doctrine in State affairs, based on legal or moral grounds.