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.
Can you target a Ring in play (at the opponent's home) with Steal an Advantage as engage?
Card Title Steal an Advantage Text This Strategy's ability is Battle/Engage if you control a Scout at this battlefield. Battle: A target enemy card may not use one of its abilities (you choose).
Rings aren't enemy cards See here: In a phrase such as "an enemy card," "enemy" does not refer to cards outside of units