I'm not sure that Congress (or at least a significant portion of it) agreed that we should attack Iraq. The AUMF was predicated on certain conditions being met that the president had to certify had been met before force could be used.

Did any of them who voted for the AUMF object at the time of the invasion on the ground that the President lacked legal authority to invade? I don't recall any of them having done so, and one certainly would expect them to if what you're saying is actually true.

I think this was perhaps best summed up by John Kerry in an interview with Rolling Stone when he said he didn't "expect George Bush to fuck it up as badly as he did". Of course that was at the end of 2003. "At the time" (March-April 2003), I don't think most realized yet how badly they'd been snookered. And in any case, no one was going to admit it at that point. This is something that con men rely on — the reluctance of the marks to make public their gullibility. Besides, it wasn't entirely clear yet that Bush had lied. Hopes of finding the WMD or of uncovering the operational links between Saddam and 9/11 were still running high. It would take years before the enormity of the con would penetrate to those who were stampeded into voting for a conditional AUMF that gave someone who had already decided months earlier to invade Iraq enough room to do so. Many still can't admit it.

He is not a general, but compare the case of 1LT Ehren Watada. He refused to deploy to Iraq with his unit, claiming that the war is illegal.

He, of course, is an exception. The vast, vast majority of the U.S. military - - as well as many other countries' militaries -- did participate in the invasion and occupation of Iraq. Are they all war criminals?

I think I've already addressed this. Principle IV of the Nuremberg Principles grants relief to those "following orders" if there is no moral choice available to them.

Also - not sure if you saw the comment I wrote to you above - but if Congress and the President both authorize a war, even an aggressive war, is it "illegal"? If your answer is that it is illegal based on treaties the U.S. signed, how about if the Congress and President abrogate those treaties?

Well, if they abrogate the treaties before engaging in their illegal war, then I would suppose the war wouldn't be "illegal". But I seem to have missed something. Did the US withdraw from the UN before invading Iraq? I know they left the ICC as soon as they decided to invade so they couldn't be tried for it and if they can't be tried for it, that makes it being illegal moot.

You may have noticed that ondelette also invoked the UN charter which is the instrument that makes "agressive war" illegal (along with the Nuremberg Principles which have been incorporated in international law (1950). The UN Charter makes it clear that use of military force except in self-defense cannot be undertaken without the approval of the UN Security Council.

The U.S. belongs to the UN by virtue of a treaty. If Congress and the President duly abrogate that treaty tomorrow, and then vote to authorize an aggressive war against Iran, is it "illegal"?

There is no mechanism for withdrawing from the UN. Much like there is no mechanism for withdrawing from the United States. So if you could explain how one goes about "duly" abrogating the UN Charter, then it might be possible to discuss the hypothetical. Otherwise, it sounds very much like one of Tiberius' typical questions. If some state, say South Carolina, decides to "duly" abrogate the Constitution can it then enter into a mutual defense treaty with the People's Republic of China?

Basically, no self-defense, no legal war without the UNSC's say-so. If the US wants to invade Iraq because it has a tyrannical leader or because it has lots of oil ("floats on a sea of it" in fact), or because its people are longing for democracy, without UNSC approval such an invasion is illegal under international law.

Bill Clinton, of course, ordered all sorts of military action, including in Yugloslavia, with no UNSC say-so. Does that make him a war criminal?

It may make the war illegal from the point of view of the UN Charter, but since the venture in Serbia/Kosovo was not a war of aggression but a "humanitarian intervention" it is not a war crime. The US had nothing in particular to gain from it. In fact, (principally Republican) congressional opposition centered on the fact the US's national interests were not involved (which is code for "Serbia has no oil"). The fact that it may have been illegal is irrelevant since the only one with jurisdiction over this is the UN and the UN has no way to impose any penalty on permanent members of the Security Council.

If by "all sorts" of military action you are referring to bombing of targets in Iraq, this came under the enforcement of UNSC resolutions stemming from GW I.

If you are including the involvement in Somalia, that was a commitment made by George H. W. Bush (in August 1992) and was part of a UN effort (UNISOM I) that began as humanitarian relief.

If there's something else that you are thinking of, it is not made particularly clear by "all sorts of military action". It pretty much falls in the same category as "many people say".