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.
A player, 20 February 2011
Just wanted to get an official ruling on this:
My opponent challenges my personality to a duel and focuses. I strike and he wins. He focused Part the Waves, so he attaches Impromtu Weapon from his discard pile. Can he now use Impromptu Weapon's reaction to gain 3?
Relevent test:
Part the Waves Text Iaijutsu Focus Effect: You may attach a Weapon from your discard pile to this Personality after this duel ends. Battle: Choose your performing unbowed Duelist: Bow a target enemy card without attachments.
Impromptu Weapon Text Weapon After this personality enters a duel: He loses Duelist until after the duel ends. Reaction: After the resolution of an action that created a duel which this Personality won: Gain 3 Honor.
Zen Faulkes (rules official), 20 February 2011
My opponent challenges my personality to a duel and focuses. I strike and he wins. He focused Part the Waves, so he attaches Impromtu Weapon from his discard pile. Can he now use Impromptu Weapon's reaction to gain 3?
Probably, but there's a lot of information missing here. For instance, it will only work if an action started the duel (to meet Impromptu Weapon's trigger), and duels are sometimes caused by things other than actions.