I am not sure whether this is a bug or not, so I'd like to know your opinion before posting it at the bug report forum. When at war with another civ and they have a suzerained city state, you can just ask that city state for peace inspite of contunuing going to war with its suzerain. Is this supposed to be like this? I think, peace should not be able as long as you're at war with a CS's suzerain.