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, 7 February 2011
I searched for Disarm to see if my question had been answered and found nothing. So if this question has already been answered, my apologies.
Disarm states:
Battle: Target your Monk: Target an enemy Personality. If he has no Weapons, reduce his force to 0. If he has any Weapons, destroy one of them. You may attach a Weapon from your hand or discard pile to your Monk.
Can this card be played on a monk that is unopposed? I've been told locally, yes, because the targetting of an enemy personality is an effect not a cost. I'd like to verify this.
Thank you for your time.
Zen Faulkes (rules official), 7 February 2011
Disarm: Can this card be played on a monk that is unopposed?
No.
http://rules.l5r.com/CE_Battles#Rule_of_Location: "A card in a unit must be at the current battlefield to be targeted by, or explicitly perform, a Battle action."
Note that it says "targeting", as in all targeting, not "targeting as a cost".