The rules relating to the prohibition on the use of force, including its exceptions, are at the core of the international legal order that emerged after the greatest human-made disaster of all times: World War II. In that legal order, peace is perceived as the main value to be protected and the prohibition on the use of force embodied in Article 2(4) of the UN Charter knows only one exception: the right of self-defense as set out in Article 51. Recourse to force in international relations is meant to be the prerogative of the Security Council. In 1945, the motto was “peace through collective security.”

What happened in this field between 1945 and 1989 is well known. It is also well known that hopes for a new peaceful international order after the collapse of communism were soon disappointed. The resort to force in international relations is even more prevalent today than it was just one decade ago. It is for this reason legitimate to inquire whether international law has undergone change in this important sphere. Since the United States has become the only superpower, since its military supremacy is overwhelming, since ultimately the United States has been one of the States that has resorted to force the most in the last decade, one is also justified in focusing on both its practice and the legal arguments it invokes, as well as the reactions of other countries to its actions and claims.