Moral Principles and their application
There's a good discussion going on in the comments to this post below, centering around the question of moral principles and how they are applied, and how each of them can be termed "official". I think a good analogy for trying to understand the difference between a principle and its application is the Church's teaching on a just wage.
The Catholic Church teaches that an unjust wage is immoral. But how is this moral principle to be applied? Good Catholics can disagree on this question of application, while they must believe in the principle of a just wage. Some Catholics -- e.g. the staffers at the USCCB -- believe that a just wage is enacted via the minimum wage. Other Catholics believe that there are better ways to apply the principle, e.g. on a case-by-case basis. Either way, the principle is held in common, while its application varies.
As far as "official" goes... every Catholic is free to seek different ways to enact a just wage in their society. When members of the Magisterium offer their views, they are simply doing what they have the right to do: argue for what they believe is the best way to enact a just wage. Some members of the hierarchy might believe that minimum wage laws are the best, but I am free to disagree with them on that (which I do), while necessarily believing that a just wage is still required.
I believe the same (or a similiar case) holds true on the matter of a war with Iraq. All Catholics must believe in the principle of a just war, but different Catholics may have different views on the application of those principles to the case of Iraq. As far as the Holy Father and other members of the hierarchy are concerned, they have just as much right as anyone else does to argue for their view in the public forum. What must be remembered is that the disagreement is over the application of a commonly-held moral principle, and when it comes to the application of a principle, legitimate disagreement (which is different from dissent, IMHO), is possible.