join_faction_with_leave_blocker_effect

join_faction_with_leave_blocker_effect = {
	join_faction = $FACTION$
	hidden_effect = {
		save_temporary_scope_value_as = {
			name = join_faction_with_leave_blocker_effect_number
			value = flag:$YEARS$
		}
		add_character_flag = {
			flag = leaving_faction_block
			years = $YEARS$
		}
	}
	if = {
		limit = { this = root }
		custom_tooltip = join_faction_with_leave_blocker_effect_first.tt
	}
	else = {
		custom_tooltip = join_faction_with_leave_blocker_effect_third.tt
	}

	#and to prevent angry error messages :D:D:D:D
	if = {
		limit = {
			scope:join_faction_with_leave_blocker_effect_number = flag:1
		}
	}
}

As written in game/common/scripted_effects/00_faction_effects.txt.