well, as far as the legal status of the attack on Iraq is concerned, since congress approved all military action, the war is certainly legal according to US law. All constitutional requirements were fulfilled.
Even if you argue that the reasons for war were false and that congress was lied to about the WMD's, that doesn't take away the fact that due process was followed when the decision to attack Iraq was made. If you wanted to argue against the reasons for going to war, you'd have to do so before a court, in this case probably the supreme court. But as far as I know, that hasn't happened yet.
The war is certainly not legal under the UN charter, since there was no attack on US soil conducted by Iraqi forces. Arguing that Iraq posed a threat to the US is ridiculous. But the UN charter doesn't matter here, because it cannot, or rather, will not be enforced anyway. In the end, all that really matters is every nation's right to protect its interests. And if that includes war, then so be it, as long as that country's laws are obeyed when the decision is made.
In other words: A soldier cannot argue that a war is illegal if his elected government has followed due process during the decision. It is not for the soldier to decide who to fight. He follows orders issued by the elected government. Democracy is a beautiful thing, isn't it ? Everybody gets the government he/she deserves....
Thus, although I admire the man's courage to stick to what he believes in, and although I personally consider the war in Iraq illegal too, he most likely has no chance legally.
Since Congress approved it, technically the war in Iraq is legal, at least according to US law.
Illegal orders are something completely different and have nothing to do with the legal status of the war as a whole. As outlined previously, if he had received an illegal order, it would have been his right, no, his duty to disobey.
But as far as I can tell, that hasn't been the case, so his ass will most likely be locked up.
Anyone who thinks that the war is illegal or based on false information should go to the guys who approved it, not let his comrades down. As an officer, he has a responsibility towards the men under his command. It would have been his job to lead them and do all he possibly can to bring them home safely. If you ask me, he is letting them down. 'Cause lord knows, they will go...