Quote Originally Posted by OA, pg 81
Focus: Both duelists make an Iaijutsu Focus check. If you do not have ranks in the Iaijutsu Focus skill, you can attempt to use the skill untrained by making a Charisma check (and you shouldn't be in an iaijutsu duel).
You can make iaijutsu focus checks untrained. I don't see any reason it would be a problem to allow it untrained. If you have no ranks you aren't going to be getting much bonus damage from it and the skill only works in extremely specifics scenarios.