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, 2 April 2013
Arcane Cloak: Other players may not target cards in this unit with actions if there are any other legal targets in this army. Broken Alliance: Battle/Open: Target an attachment and pay Gold equal to its Gold Cost minus two: Destroy it. A Stain Cleansed: Choose your performing unbowed Magistrate, target an enemy card without attachments or an enemy unit, and pay Gold equal to the card or unit's total Gold Cost minus 2: Destroy it. Yoritomo Hiromi: Battle: Target an enemy card without attachments, or an enemy unit, with a lower total Gold Cost than Hiromi's unit: Hiromi strikes with the power of Thunder. Destroy the target.
So the 1st Question is: If my opponent has 2 personalities one with the Arcane Cloak attached and another with say Wyrmbone Katana attached. If I only have 2 gold open, can I target the Cloak since I can't pay the Katana's Gold Cost minus 2? Or in rules terms: Is a card considered a legal target for a card that requires me to pay gold, IF I can't pay the required gold?
How does the following situation play out: My opponent has 2 different 7 gold Scorpion Personalities in play. 1 is equipped with Arcane Cloack and 1 is equipped with Wyrmbone Katana. I only have 8 gold unbowed. Can I use the Unit Targeting on A Stain Cleansed to destroy the unit with the Armor, or do I have to choose the card destruction and the Wyrmbone? Would the ruling Change if I tried using Yoritomo Hirmoi instead of Stain Cleansed (since it's not an issue of being able to pay the gold)?
Also, follow up question: An "Army" only exists if a battle is being fought, Correct? So I could just target the Cloak with Broken Alliance's open action regardless of the rulings above.
A player, 2 April 2013
Is a card considered a legal target for a card that requires me to pay gold, IF I can't pay the required gold?
The target is legal if it fulfils the conditions in card text and rules. In this case, it has to be a "card without attachments in an enemy unit". Thus the target is legal. However, if you can't pay the gold for the target you've chosen, the Good Faith Rule forbids you to choose that target. It's not a matter of target legality, but rather of action legality. The target is still legal to choose, but you can't pay the bill.
Edit: That's also why your opponent can interfere with targets and choose one target so expensive you can't pay for the new cost, in order to force your action to fail. Because targets and costs are different things, and target legality is independent of you being able to pay the associated cost.
My opponent has 2 different 7 gold Scorpion Personalities in play. 1 is equipped with Arcane Cloack and 1 is equipped with Wyrmbone Katana. I only have 8 gold unbowed. Can I use the Unit Targeting on A Stain Cleansed to destroy the unit with the Armor, or do I have to choose the card destruction and the Wyrmbone?
The Wyrmbone Katana is a legal target for A Stain Cleansed, so the Arcane Cloak isn't an option for you.
Would the ruling Change if I tried using Yoritomo Hirmoi instead of Stain Cleansed (since it's not an issue of being able to pay the gold)?
No, because this is not negation but choice restriction. Your action goes through and has full effect, you simply can't choose the target you'd like to.
Also, follow up question: An "Army" only exists if a battle is being fought, Correct? So I could just target the Cloak with Broken Alliance's open action regardless of the rulings above.
Not exactly. An Army only exists at a side of a battlefield. Even if the battle is not being fought, the army still exists. However, if the unit is at home, either because it didn't assign, or it moved, or it's the Action Phase, it's not in an army, and therefore can be targeted by actions, such as the Open action from Broken Alliance. Which I'd bet is the most common demise of the Arcane Cloak...