The just war tradition has been considered a major perspective on the ethics of war since the writings of St. Augustine were rearticulated by Thomas d 'Aquinas. It attempts to provide a framework that validates just conflict, while enforcing limits to prevent unrestrained war. Today, its fundamental principles can be divided into two broad categories: “jus ad bellum” (just use of war) and “jus in bello” (just conduct in war). For a war to be just, many criteria must be met within these categories. In recent decades, non-state terrorism has become increasingly publicized; in fact, in the 21st century, this issue has dominated the global political agenda. It is therefore pertinent to ask whether terrorism can be ethically assessed using the just war tradition. In this essay, I will argue that it is possible to ethically evaluate terrorism using just war principles. I will show that terrorists can meet the most important criterion of the just war tradition. First, they may represent “legitimate authority” and have a “just cause.” Second, terrorism can be a “last resort” and offers a “reasonable prospect of success.” Finally, although many terrorists adhere to the principle of “discrimination,” the notion of “noncombatant immunity” and civilian innocence is too simplistic. Additionally, terrorists may consider themselves to be in a "supreme emergency," meaning that the rules of war cease to exist. Terrorism can satisfy the principle of proportionality. However, before I begin my argument, I must establish a working definition of “terrorism”; an important and controversial issue in itself. Walzer describes it as "like rape and murder...an attack on innocent people" (2005... middle of article...... Family Research Council, accessed online: 07/11/2010Roberts, Adams, (1989), “Ethics, Terrorism and Counterterrorism”, Terrorism and Political Violence 1 (1), pp. 48-70 Schmidt Alex P and Jongman Albert I, (1998) “Political Terrorism” (Amsterdam, Transaction Books) Smilanski , Saul, (2004), “Terrorism, justification and illusion”, Ethics, 114, July pp. 790-805Valls, Andrew, (2000), “Can terrorism be justified”, In Andre Valls (ed.), Ethics in International Affairs, pp. 65-80Walzer, Michael, (1992), “Just and Unjust Wars: A Moral Argument with Historical Illustrations”, (New York: Basic Books)Walzer, Michael, (2005), “Arguing About War”, (Yale Nota Bene )Wilkins, Burleigh Taylor, (1992), “Terrorism and collective responsibility”, (New York: Routledge)US Department of State, (2005), “Country Reports on Terrorism”, consulted online: 15/11/2010