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.
In this thread...
... I think the original poster is asking whether Battle (not just Battle/Open) actions are legal during an Ambush, since nothing explicitly suspends the rule that says Battle actions are not legal during the Action phase.
(if this is the case, then I'd surely like to know - making it almost impossible to act during an Ambush would push the card back into high power zone)
In this thread...
... I think the original poster is asking whether Battle (not just Battle/Open) actions are legal during an Ambush, since nothing explicitly suspends the rule that says Battle actions are not legal during the Action phase.
(if this is the case, then I'd surely like to know - making it almost impossible to act during an Ambush would push the card back into high power zone)
The rules for fighting a battle are detailed at http://rules.l5r.com/Battles . Fighting a battle is one of the effects that Ambush resolves. No players are able to take Limited or Open actions while the effects of the current Limited action (ambush) resolve, just like no player is able to take a Limited or Open action while any other Limited action's effects are resolving. Since the "fight a battle" effect of Ambush takes you through a Combat Segment, players are able to take Battle and Battle/Open actions during that Combat Segment. There is no "Attack Phase" or "Declaraction Segment", and your Maneuvers segments are forced by Ambush text (third paragraph of the Battles CR entry linked above). This means that no allies may be called, and cards that react to an Attack Phase (such as Retribution) may not be played in response to an Ambush. There is only one battlefield to choose from (the Ambush battlefield), as the battlefields at provinces would be created during the Declaration Segment of the Attack Phase, which Ambush does not have. Since the battlefield is not associated with any province, no province will be destroyed due to combat resolution of an Ambush battle.
I think this covers most of the loopholes that people are trying to find with Ambush.