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, 30 July 2007
So if I'm reading this right: http://www.alderac.com/forum/viewtopic.php?f=59&t=59770
1) Suppose I'm the Unicorn defender. The active Scorpion player moves Bayushi Muhito into a battle opposing my Unicorn personality. Active player reacts and says "I choose to take an additional action" (this is a delayed effect) I (Unicorn player) play Cut Them Off to bow Muhito. Scorpion player then takes his additional action. Bayushi Muhito Reaction: After an action resolves that moved Muhito to or from a battlefield: Take an additional Battle action. Is this correct?
2) Suppose my opponent moves Fusami into a battle opposing me and I play Cut Them Off. Does Fusami get to issue her challenge? (I'd guess yes as the rule just doesn't allow her to use the ability when bowed, but the ability has been activated already.) Fusami Reaction: After another player's target Personality assigns or moves to an army attacking you: Fusami moves to the target's location and challenges him. The challenge may be refused; if it is refused, bow the target and move him home. Destroy the loser. Thanks, Leon
Martin Lund (rules official), 31 July 2007
So if I'm reading this right: http://www.alderac.com/forum/viewtopic.php?f=59&t=59770
1) Suppose I'm the Unicorn defender. The active Scorpion player moves Bayushi Muhito into a battle opposing my Unicorn personality. Active player reacts and says "I choose to take an additional action" (this is a delayed effect) I (Unicorn player) play Cut Them Off to bow Muhito. Scorpion player then takes his additional action. Bayushi Muhito Reaction: After an action resolves that moved Muhito to or from a battlefield: Take an additional Battle action. Is this correct?
Yes. You have to wait until someone would normally be given the priority to take a Battle Action before any "additional battle actions" can be taken. That means the previous Battle Action and its Reactions have to all be dealt with first.
2) Suppose my opponent moves Fusami into a battle opposing me and I play Cut Them Off. Does Fusami get to issue her challenge?
You can't play Cut Them Off until Fusami's Reaction has finished Resolving. That means not only the movement portion of its effects, but also the Challenge. Cut Them Off says, "After an action resolves that moved ..." Someone's going to get dueled long before you can play Cut Them Off.