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 question came up while playing tonight. Can I Hamstrung someone if I have no presence? I am led to believe I can since its negating the action before he moves. Example: at the current battlefield person A has 1 bowed attacker. Person B has no defenders. Person A tries to move an unbowed attacker in the battle from home. Person B plays Hamstrung to negate the movement.
I have to think this would work because the person is at home, its impossible for me to have presence there anyway.
Reactions are not governed by the rules of Presence and Location, they affect Battle actions only. As a consequence, you can take Hamstrung's Reaction even if you control no unit at the current battlefield and even if this action targets a Personality who is not there.
Battles, Combat Segment: "Reactions are not subject to rules of Presence and Location."