I'm running a nice empire with, as any self respecting Emperor would require, absolute crown authority. The wiki says:
Vassals can no longer go to war (except to rebel) at all ... It also does not work for any king vassal unless they are your de jure vassal.
I have several King vassals who wage quite a lot of wars on each other, vassals, and outsiders. If I wanted to keep all of my Kings at constant peace, would I have to hold the de jure Empire title above them? E.g. Hispania for Leon, Castille, Navarra et al, Francia for France, Aquitane, Bhriotáin and Brugundy. So far, only the Holy Roman Empire and Byzantine Empire exist, so it feels very weird to have vassals beholden to crown laws under nonexistent empire titles.
Can Kingdoms ever assimilate into Empires? If this were to occur, would they finally be under my crown authority?
I noticed that I can set the Crown Authority for each of my Kingdom titles independently; I gather that my vassals have that authority as well. What would the impact be if they had a lower crown authority than mine? Their vassals would be able to declare war, yes? Would they be able to declare on just other vassals of their liege or would they be able to target my other vassals?