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, 16 September 2007
I am still a bit confused about the timing.
Reinforce the Gates: Reaction: After a player announces a Battle action before the Defender’s first normal opportunity to act or pass: Negate the action’s effects.
So if an attacker attacks and uses the Naval (or Sneak Attack) effect, can the defender wait until after the subsequent action is announced before he plays the Reinforce the Gates to negate the effect?
In my previous question, the example I used was with a Naval personality with a Battle: bow for a Range 3 attack.
Could the defender let the attacker announce and use the Naval ability. Then after he bows the personality for the range 3 attack, use Reinforce the Gates which will negate the range 3 attack and leave the personality bowed?
Zen Faulkes (rules official), 16 September 2007
So if an attacker attacks and uses the Naval (or Sneak Attack) effect, can the defender wait until after the subsequent action is announced before he plays the Reinforce the Gates to negate the effect?
Not only can the defender wait, the defender must wait. Neither the Naval ability nor Sneak Attack is a legal trigger for Reinforce the Gates because they are not Battle actions.