bannable_serving_diarch_trigger

bannable_serving_diarch_trigger = {
	liege ?= {
		NOR = {
			is_landless_adventurer = yes
			has_diarchy_type = grand_secretariat
		}
	}
	OR = {
		# Diarchs with official responsibilities can't come out to play.
		is_diarch = yes
		is_designated_diarch = yes
		# Assumed diarchs don't get to either if they're the AI, as the player might be planning around them & the AI may have designated to avoid people after if it'd known they were going to welch.
		## Assumed-diarch players can make an intelligent choice on whether they want to go to events or not.
		AND = {
			is_ai = yes
			is_diarchy_successor = yes
		}
	}
}

As written in game/common/scripted_triggers/00_diarchy_scripted_triggers.txt.