I. LAW V. JUSTICE
Many theologians, ethicists, political scientists and occasionally even international lawyers would like to revive the "just war" (bellum justum) doctrine in present-day international law. This doctrine was prevalent in the writings of the "fathers of international law" in the sixteenth through the eighteenth centuries. It was borrowed from the Church canonists. Although the roots of the doctrine go back to St. Augustine (early in the fifth century), (1) its principal expression is the Thomist analysis (in the thirteenth century). St. Thomas Aquinas held that a "just war" had to satisfy three cumulative conditions: (i) the authority of a prince (auctoritas principis); (ii) a just cause (causa justa); and (iii) righteous intention (intentio recta). (2)
Through the writings of the "fathers of international law"--Victoria (who, not coincidentally, was a Spanish Dominican monk) and others--the Thomist ideas percolated from theology into the Law of Nations. But it is important to bear in mind that, from the very beginning, the list of "just causes" was manipulated by the "fathers of international law" to fit the political needs of their respective countries. Thus, Victoria--in addressing Spain's war against the "Indians" in the New World--upheld the justice of that war on the made-to-measure excuse that the Indians had violated the Spaniards' right to travel freely, to carry out trade, and to propagate Christianity. (3)
Even in its heyday, the "just war" doctrine was mostly a convenient tool or fig-leaf, and States went to war whenever they deemed fit, using or abusing an arbitrary list of "just causes." There is no indication whatever that the "just war" doctrine affected the practice of States by limiting in a perceptible manner their freedom to go to war. No wonder that, by the nineteenth century, the international legal literature abandoned the "just war" doctrine and openly admitted that States had full discretion to "resort to war for a good reason, a bad reason or no reason at all." (4) Through bilateral non-aggression pacts, States could relinquish in individual cases their general right to go to war. But, otherwise, war could be waged whenever it was considered advantageous.
International law underwent a metamorphosis only in the twentieth century: first (in a somewhat restricted fashion) in the 1928 Kellogg-Briand Pact for Renunciation of War as an Instrument of National Policy, (5) and then--in a sweeping prohibition of the use (and even the threat) of force in international relations--in Article 2(4) of Charter of the United Nations of 1945. As proclaimed by the International Court of Justice, in 1986, in the Nicaragua case, this prohibition is now reflected in customary international law. (6)
There is no reason to think that the congruence of Charter and customary law on the use of force has disintegrated between 1986 and 2003. Can future customary international law part company in this regard with the law of the Charter? In theory, the answer to the question is affirmative. But one must keep in mind that the interdiction of the use of inter-State force is generally acknowledged today as jus cogens (a peremptory norm). (7) A revision of jus cogens--albeit feasible--is not easy to bring about. (8)
The overall prohibition of the use of inter-State force is subject to only two exceptions, both explicitly recognized in the Charter: (a) self-defense in response to an armed attack, (9) and (b) military action taken or authorized by the Security Council in a binding decision, following determination of the existence of a threat to the peace, a breach of the peace, or an act of aggression. (10)
The powers of the Security Council pursuant to the Charter are extensive, but--unless the five Permanent Members (vested with a veto power) are willing to put these powers in play the Security Council may remain aloof (not to say paralyzed) notwithstanding a manifest need for action. …