US at Nuremberg: "no grievances justify aggressive war"

US Supreme Court Justice Robert H. Jackson, Chief Counsel for the United States at the Nuremberg Trials, said in a statement to the American people:

We must make clear to the Germans that the wrong for which their fallen leaders are on trial is not that they lost the war, but that they started it. And we must not allow ourselves to be drawn into a trial of the causes of the war, for our position is that no grievances or policies will justify resort to aggressive war. It is utterly renounced and condemned as an instrument of policy.

I therefore want to make clear to the American people that we have taken an important step forward...in fixing individual responsibility of war-mongering, among whatever peoples, as an international crime.

In a report to the President, he added:

By the time the Nazis came to power it was thoroughly established that launching an aggressive war or the institution of war by treachery was illegal and that the defense of legitimate warfare was no longer available to those who engaged in such an enterprise. It is high time that we act on the juridical principle that aggressive war-making is illegal and criminal.

The reestablishment of the principle of unjustifiable war is traceable in many steps. One of the most significant is the Briand-Kellogg Pact of 1928, by which Germany, Italy and Japan, in common with ourselves and practically all the nations of the world, renounced war as an instrument of national policy, bound themselves to seek the settlement of disputes only by pacific means, and condemned recourse to war for the solution of international controversies. Unless this Pact altered the legal status of wars of aggression, it has no meaning at all and comes close to being an act of deception. In 1932, Mr. Stimson, as Secretary of State, gave voice to the American concept of its effect. He said, "War between nations was renounced by the signatories of the Briand-Kellogg Treaty. This means that it has become illegal throughout practically the entire world. It is no longer to be the source and subject of rights. It is no longer to be the principle around which the duties, the conduct, and the rights of nations revolve. It is an illegal thing. . . . By that very act, we have made obsolete many legal precedents and have given the legal profession the task of re-examining many of its codes and treaties."

This Pact constitutes only one in a series of acts which have reversed the viewpoint that all war is legal and have brought International Law into harmony with the common sense of mankind, that unjustifiable war is a crime. Without attempting an exhaustive catalogue, we may mention the Geneva Protocol of 1924 for the Pacific Settlement of International Disputes, signed by the representatives of fortyeight governments, which declared that "a war of aggression constitutes ... an international crime". The Eighth Assembly of the League of Nations in 1927, on unanimous resolution of the representatives of forty-eight member nations, including Germany, declared that a war of aggression constitutes an international crime. At the Sixth Pan-American Conference of 1928, the twenty-one American Republics unanimously adopted a resolution stating that "war of aggression constitutes an international crime against the human species."

So, under several treaties to which the US is party, and under generally recognized international law, if the war against Iraq was a war of aggression (and granted, that's a big "if"), then it is an illegal war, and those who perpetrated it are war criminals.