There have been many wars fought in real life that had no justifiable reason for war. While a CB here is generally required in order to garner favor with ones allies in order to procure defensive and offensive support there is no actual need for a cb.
The CB as it pertains to our current situation is truly a PR tool and nothing more angst it is one that no matter how cut and dry will always be hotly contested by one or more sides in the war.
I for one would not engage in an offensive (alliance wide)conflict without a valid CB but I don't think it is a requirement for one aa to attack another. I may not agree with ds attacking invicta or goons "raiding" micros (yes same thing no matter how you spin it) but I commend them for conducting themselves as a sovereign entity should, how they see fit for themselves.
If only more alliances acted as such and threw their care for pr aside to settle whatever grudges they harbor. This convoluted treaty Web would reset itself.