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 June 2008
Can Doji Sakurako cancel the effects of:
1. Attacker's Terrains placed by Untested Scouts
2. Attacker's Terrains placed by Removing the Advantage
Would her ability apply in the same situation if she is in the Attacking army and the Defender used those cards?
Doji Sakurako - Political Reaction: After a player announces a Battle action before the Defender's first normal opportunity to act or pass, if Sakurako is at the current battlefield, discard the Imperial Favor: Negate the action's effects.
Untested Scouts - Recon Limited: Target a Province. Until the turn ends, after engaging in a battle at the province's battlefield, you may take one additional Battle action to play a Terrain from your hand.
Removing the Advantage - Reaction: After engaging in a battle, if you control a unit at the current battlefield: Play a Terrain card as an additional Battle action.
Alex Jones (rules official), 17 June 2008
Can Doji Sakurako cancel the effects of:
1. Attacker's Terrains placed by Untested Scouts
2. Attacker's Terrains placed by Removing the Advantage
Would her ability apply in the same situation if she is in the Attacking army and the Defender used those cards?
Doji Sakurako - Political Reaction: After a player announces a Battle action before the Defender's first normal opportunity to act or pass, if Sakurako is at the current battlefield, discard the Imperial Favor: Negate the action's effects.
Untested Scouts - Recon Limited: Target a Province. Until the turn ends, after engaging in a battle at the province's battlefield, you may take one additional Battle action to play a Terrain from your hand.
Removing the Advantage - Reaction: After engaging in a battle, if you control a unit at the current battlefield: Play a Terrain card as an additional Battle action.
Untested Scouts and Removing the Advantage both grant additional Battle actions with timing points sometime between "Armies Engage" and the "Defender's first normal opportunity". Doji Sakurako's Reaction can thus be performed in response to them; she doesn't care whether the action is performed by the attacker or the defender.
The Defender will usually have trouble playing a terrain from Untested Scouts, however, since its ability is Limited.