Well sort of, the option to disable it is called to the flory of god reformation belief. But serious answer is chain citadel them yourself first (GG bonus is not really substantial, protecting horses and especially coal, aluinium, and uranium, or monopoly granting lux tiles is). and it's gimmicky but I am nearly sure that even if it isn't the rule I was sometimes blocked from citadeling by fort configuration on enemy side (grayed out option despite not being next to another citadel). I started to actually make many forts on the frontier from when I first saw it and it's actually working.