I can think of some exceptions to my general rules. For example, let's say a civil war has erupted in a state between two ethnic groups and, depending on the outcome of that conflict, a neighboring state would be at credible and imminent risk of conflict among its own population. In that case, I believe military intervention could be justified. Moreover, in such circumstances, I reject the Walzer idea that such intervention should not be so decisive as to alter the outcome of that civil conflict, even if that outcome runs counter to the self-determination of the majority of people in that state. A state's highest duty is to its own security and existence, not the self-determination of people in a neighboring state when there is a conflict between the two.
My view is that military intervention aimed at preventing/stopping genocide offers the clearest-cut example where a humanitarian cause could be sufficient to justify military intervention. Even there, some additional flexibility could exist e.g., if a government's actions are creating a significant flow of refugees into a neighboring state and such a development is at credible and imminent risk of destabilizing that neighboring state. So, in theory, there might be exceptional circumstances where subjugation could play a role, but my guess is that such circumstances would be rare.That sounds like a pretty all-inclusive statement to me.
If it was not all-inclusive, then that would mean that given the right set of national interests, going to humanitarian intervention on the basis of subjugation might be reasonable. So you think Iraq war was justified?
My worry about extending humanitarian military interventions to cover all forms of subjugation is that such criteria is overly broad and could be exploited for malevolent purposes. Such assured broad latitude for justifying conflict could well morph into license for would-be aggressors to advance valid justification under which they could cloak their aggression. It could also lead make it too easy for there to be forceful interference in other states' internal affairs. Either outcome could, in the whole scheme of things, lead to greater instability, more frequent conflict, and net overall costs.
My opinion is that much narrower criteria would be better, allowing for some flexibility on a case-by-case basis where extenuating circumstances exist. I provided two examples. However, my guess is that the overwhelming number of situations would not produce such extenuating circumstances. Hence, my framework--and such framework is my personal opinion, only--would apply to the vast majority of cases where one seeks to evaluate whether military intervention could be legitimate.
As for Iraq, my view is that although there was a credible threat (as per the Intelligence assessments at the time, which turned out to be incorrect) but not an imminent one (something the intelligence assessments got correct) and there was no ongoing or credible and imminent threat of genocide, the war would not qualify as "just" under my framework. Needless to say, error does not invalidate a conflict's nature, as perfection cannot be the standard by which human decisionmaking is judged. With respect to Iraq, I can't think of extentuating circumstances that might change my assessment.