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, 19 February 2009
Hey all, If my opponent destroys a spell at a battlefied and I have a unused Fortified Camp and a straightened Isawa Chinatsu who has not used her ability that turn, will her reaction pay to reattach the spell?
A. Yes B. No, because the cost is actually being generated by the Fortified Camp's Reaction, much the way you cannot use the benefit of a Supply Outpost trait benefit when paying for a personality without gaining honor to attach a Warden for 2 honor.
Fortified Camp: Bow this card: Produce 2 Gold, or produce 3 Gold if paying for an attachment. Reaction: After another player’s action destroys one of your attachment cards or it’s Personality: Attach the card to one of your target Personalities (paying all costs).
Isawa Chinatsu: Reaction: When paying for a Spell: Produce 2 Gold.
[Deleted Formatting; Red-colored text is only for Mod use. -- MB2001]
Brook Cunningham (rules official), 20 February 2009
Hey all, If my opponent destroys a spell at a battlefied and I have a unused Fortified Camp and a straightened Isawa Chinatsu who has not used her ability that turn, will her reaction pay to reattach the spell?
A. Yes
The answer is:
A. Yes, you could choose to use her Reaction to pay for the Spell.
The answer is not:
B. No, because the cost is actually being generated by the Fortified Camp's Reaction, much the way you cannot use the benefit of a Supply Outpost trait benefit when paying for a personality without gaining honor to attach a Warden for 2 honor.
...because the issue with Supply Outpost's trait versus Wardens' Reaction is that both effects attach the card; you have to choose to do one or the other. Then, after it's attached, you can't have another effect try to attach it again because it's no longer in your hand (as each effect requires).
Conversely, Fortified Camp's effect attaches, and Chinatsu produces Gold. These effects don't conflict or invalidate one another; they actually go quite well together.