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, 27 January 2010
I'm aware that an update to CE compliant Legacy rules is forthcoming. Hopefully by asking this now, rather than then, some strangeness in the rules set can be avoided. In short, under the current Legacy rules it appears to be possible for a card to have, or not have, keywords based on which other cards are interacting with it at the time. For example, let's take a Legacy Naga deck:
Heart of the Shinomen Forest Stronghold: Naga (3FH / 3GC / 5PS) Your Nagas are immune to Fear. You may ignore Honor Requirements for Nagas if you have no Shadowlands cards in play. You may have up to 4 of any non-unique Naga card. You may put forests into play for 3 less gold. MRP: Hidden Emperor 1
Forest Killer Cavern Holding (2G) Bow this card: Produce 2 Gold equal plus 1 Gold for each Wealth token on this card. Limited: Dishonor one of your target Personalities: Add a Wealth token to this card. You may target another player's Holding and remove a Wealth token from it. MRP: Samurai Edition
Forests of Shinomen Region Forest Negate the effects of Ranged Attacks during a battle at this province's battlefield. When one of your Forests is paying for a Nonhuman card: It produces one additional Gold. MRP: Celestial Edition
Yuki no Onna Personality (1F / 2C / 0HR / 6GC / 1PH) Unaligned Snow Maiden. Nonhuman Yuki no Onna gains +1F/+1C for each Forest in play. Limited: Yuki no Onna bows to challenge a Shadowlands Personality. The challenge is unrefusable if the the Personality's controller controls any Forests. MRP: Gold Edition
From the Older Cards section of the Legacy Rules, "for cards printed prior to Khan's Defiance ... [c]ard titles also count toward determining keywords. This is true when determining an older card’s keywords and when an older card is looking for keywords." This results in some very strange interactions. Heart of the Shinomen Forest was printed prior to Khan's Defiance. Therefore, it searches in the titles of cards printed after Khan's Defiance to locate keywords. It therefore concludes that Forest Killer Cavern is a forest, and allows the naga player to bring it into play for 3 less gold. However, both Forest Killer Cavern itself and the Forests of Shinomen region have their most recent printing after Khan's Defiance. Therefore, that Legacy rule does not apply (neither is an "older card", nor is an "older card" looking for keywords), so keywords are determined normally under the CE rules set. Forest Killer Cavern is no longer a forest, and does not produce an additional gold when paying for the cost of a Nonhuman card. But, at the same time, it is a forest, contributing to the continuous bonus of the pre-Khan's Defiance card Yuki no Onna.
This makes determining the game state really complicated! (And believe me, this isn't the weirdest set of interactions possible.)
Finally, a tangentially related question of clarification regarding the "Stronghold Immunity" rule in the CE comprehensive rules. "Stronghold Immunity: effects, costs, and targeting applied to "cards," or referring to a particular keyword that a Stronghold has, do not legally apply to a Stronghold unless they specifically mention the word "Stronghold," or come from the Stronghold itself. Strongholds count as cards in all other ways." Both Forests of Shinomen and Yuki no Onna believe that Heart of the Shinomen Forest has the forest keyword due to its title, based on the Legacy rule. However, I am unclear how they would interact with the Stronhold Immunity rule. I suspect that stronghold would not produce an additional gold (for Nonhuman cards) when Forests of Shinomen is in play, because its trait would change the capabilities of the stronghold, and is therefore a prevented effect, but that Yuki no Onna would count the stronghold for determining her continuous bonus, because her trait is not affecting the stronghold and is therefore not "appl[ied] to" it (similar to the interaction of several Mantis strongholds with things that trigger off the port keyword).
Alex Jones (rules official), 27 January 2010
I'm aware that an update to CE compliant Legacy rules is forthcoming. Hopefully by asking this now, rather than then, some strangeness in the rules set can be avoided. In short, under the current Legacy rules it appears to be possible for a card to have, or not have, keywords based on which other cards are interacting with it at the time. For example, let's take a Legacy Naga deck:
Heart of the Shinomen Forest Stronghold: Naga (3FH / 3GC / 5PS) Your Nagas are immune to Fear. You may ignore Honor Requirements for Nagas if you have no Shadowlands cards in play. You may have up to 4 of any non-unique Naga card. You may put forests into play for 3 less gold. MRP: Hidden Emperor 1
Forest Killer Cavern Holding (2G) Bow this card: Produce 2 Gold equal plus 1 Gold for each Wealth token on this card. Limited: Dishonor one of your target Personalities: Add a Wealth token to this card. You may target another player's Holding and remove a Wealth token from it. MRP: Samurai Edition
Forests of Shinomen Region Forest Negate the effects of Ranged Attacks during a battle at this province's battlefield. When one of your Forests is paying for a Nonhuman card: It produces one additional Gold. MRP: Celestial Edition
Yuki no Onna Personality (1F / 2C / 0HR / 6GC / 1PH) Unaligned Snow Maiden. Nonhuman Yuki no Onna gains +1F/+1C for each Forest in play. Limited: Yuki no Onna bows to challenge a Shadowlands Personality. The challenge is unrefusable if the the Personality's controller controls any Forests. MRP: Gold Edition
From the Older Cards section of the Legacy Rules, "for cards printed prior to Khan's Defiance ... [c]ard titles also count toward determining keywords. This is true when determining an older card’s keywords and when an older card is looking for keywords." This results in some very strange interactions. Heart of the Shinomen Forest was printed prior to Khan's Defiance. Therefore, it searches in the titles of cards printed after Khan's Defiance to locate keywords. It therefore concludes that Forest Killer Cavern is a forest, and allows the naga player to bring it into play for 3 less gold. However, both Forest Killer Cavern itself and the Forests of Shinomen region have their most recent printing after Khan's Defiance. Therefore, that Legacy rule does not apply (neither is an "older card", nor is an "older card" looking for keywords), so keywords are determined normally under the CE rules set. Forest Killer Cavern is no longer a forest, and does not produce an additional gold when paying for the cost of a Nonhuman card. But, at the same time, it is a forest, contributing to the continuous bonus of the pre-Khan's Defiance card Yuki no Onna.
This makes determining the game state really complicated! (And believe me, this isn't the weirdest set of interactions possible.)
Finally, a tangentially related question of clarification regarding the "Stronghold Immunity" rule in the CE comprehensive rules. "Stronghold Immunity: effects, costs, and targeting applied to "cards," or referring to a particular keyword that a Stronghold has, do not legally apply to a Stronghold unless they specifically mention the word "Stronghold," or come from the Stronghold itself. Strongholds count as cards in all other ways." Both Forests of Shinomen and Yuki no Onna believe that Heart of the Shinomen Forest has the forest keyword due to its title, based on the Legacy rule. However, I am unclear how they would interact with the Stronhold Immunity rule. I suspect that stronghold would not produce an additional gold (for Nonhuman cards) when Forests of Shinomen is in play, because its trait would change the capabilities of the stronghold, and is therefore a prevented effect, but that Yuki no Onna would count the stronghold for determining her continuous bonus, because her trait is not affecting the stronghold and is therefore not "appl[ied] to" it (similar to the interaction of several Mantis strongholds with things that trigger off the port keyword).
Under discussion.
Note that Yuki no Onna does not count Heart of the Shinomen Forest as a Forest for her bonus because it is an "effect ... referring to a particular keyword that a Stronghold has".