Just War?

Many have been wondering if the impending war on Iraq could be called just or ethical. C.S. Lewis says that patriotism is a far better reason for going to war than ethics (although it shouldn't replace ethics):

Rulers must somehow nerve their subjects to defend them or at least to prepare for their defence. Where the sentiment of patriotism has been destroyed this can be done only by presenting every international conflict in a purely ethical light. If people will spend neither sweat nor blood for 'their country' they must be made to feel that they are spending them for justice, or civilisation, or humanity. That is a step down, not up. Patriotic sentiment did not of course need to disregard ethics. Good men need to be convinced that their country's cause was just; but it was still their country's cause, not the cause of justice as such. (C.S. Lewis, The Four Loves)

Lewis argues that there's a difference between a purely ethical war, and a patriotic war that is also ethical. America is arguing that it is about to wage a war for the cause of justice, not for its own sake. Is Lewis right? What does this mean for the war on Iraq?