Medium crown law not preventing vassals from fighting

[Kavok]

I've got pretty much all the king titles in Spain at this point, but my dukes keep warring with each other. I've even upped to high for crown law and they STILL press claims against each other and fight.

I thought medium was supposed to stop that? It becomes nearly impossible to prevent one duke from getting too powerful.

 

[londoner247]

Probably a silly question but have you checked each of your separate Kingdoms to make sure that you have medium (or high) crown laws in each Kingdom?

 

[Zarine]

Pretty sure a vassal of Leon can attack a vassal of Castille and this might be your problem.

 

[K-vald]

Have you checked the previous suggested occasions and if you have and there's still a problem, can you submit a save file of the issue?