There's no diplomatic option to tell them to leave as in the Civ games.Once i see that happening i usually take it as a sign that that faction has little regard for me and war maybe looming.
I usually send a diplomat to them.In my current game as the English the French,who were my allies,were doing that a lot around Caen.When my diplomat approached them their priority was 'war'.Sure enough a few turns later....
Bookmarks