Quote Originally Posted by Dîn-Heru
How many cardinals do you have compared to them?
That shouldn't matter. There's too many wars for the pope to interfere in every one. But when he does...

When he warns you to stop fighting, say Milan then he warns them too. If they keep fighting then they get excommed.

NOTE: Whoever is attacking is punished. Not defending. So you can sally, but you can't besiege. Your cities count from the turn the warning was given: If Milan take a city, you besiege it to get it back next turn then the pope says stop fighting then you can't take it back.