Full Idea
There is a paradox if the unjust are justified in fighting the just in order to protect their own civilians who have been endangered by the starting of an unjust war.
Gist of Idea
Can an army start an unjust war, and then fight justly to defend their own civilians?
Source
Jeff McMahan (Killing in War [2009], 2.1)
Book Reference
McMahan,Jeff: 'Killing in War' [OUP 2009], p.49
A Reaction
[my summary of MacMahan pp.48-49] It suggests that in a war there may be local concepts of justice which are at odds with the general situation - which is the ad bellum/in bello distinction. But this is the justice of fighting, not how it is conducted.