Roman Empire Restored problem

[sueil]

So I have conquered all the territories needed to restore the Roman Empire as Byzantium yet it won't let me because it says I don't control the Duchy of Antioch. All 4 provinces part of that duchy are under Byzantium control as well as the 3 du jure. Am I missing something? The guy that owns all that territory is my direct vassal.

edit: Seems I found the problem. That Assassin Guild took control of one of the mosques there. How can I get it back?

 

[unmerged(29774)]

click on the little circle/shield for the mosque, click on the rulers face, if he has a liege click on his face, declare war

 

[nate10101]

You should have a CB to take the holding as long as you (or a vassal) holds the county.