A topic from AEG's L5R CCG Rules forum, copied for Oracle of the Void from a copy of the forum saved in October 2015, so pages it didn't save are missing. Players' names are left out; the rules officials are named. Rulings are as they stood on these dates; later rulings, the rulebooks and the Rules Archive may differ.
Rights of the Challenged Reaction: When one of your Personalities is challenged to a duel, your Personality has the first option to focus or strike, regardless of other effects. Compare Chi versus Chi; adjustments made during the duel apply to Chi.
Does the Duelist trait count as an effect and does this card prevent a duellist who challenges someone with higher chi from focusing first?
Rights of the Challenged Reaction: When one of your Personalities is challenged to a duel, your Personality has the first option to focus or strike, regardless of other effects. Compare Chi versus Chi; adjustments made during the duel apply to Chi.
Does the Duelist trait count as an effect and does this card prevent a duellist who challenges someone with higher chi from focusing first?
Having the Duelist keyword does indeed lead to an effect that comes from the rulebook. So, yes, Rights of the Challenged would prevent a challenging Duelist from focusing first.