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, 14 July 2010
Iuchi Quan: Recon Limited: Target a province. Quan divines the landscape. After the next Cavalry Maneuvers Segment this turn you may assign a unit (with an unbowed Personality) to that province's battlefield.
Plans within Plans: Open: Play during another player's Action Phase. At your next opportunity to take an Open action, you may instead take a Limited action. Effects that last until one of "your" phases ends, end during the appropriate phase this turn.
On an opposing players turn, if I use Plans within Plans and then on my next action use Iuchi Quan targeting one of the opponent's provinces, can I assign a unit to that province (by Quan's ability) if the opponent declares an attack? If I can, would the opponent then have to resolve that province?
Zen Faulkes (rules official), 14 July 2010
On an opposing players turn, if I use Plans within Plans and then on my next action use Iuchi Quan targeting one of the opponent's provinces, can I assign a unit to that province (by Quan's ability) if the opponent declares an attack?
No. There is no battlefield to assign to. Battlefields only exist at the defender's province. http://rules.l5r.com/CE_Sequence_of_pla ... on_Segment
(Seriously, did you expect any other answer?)