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, 25 March 2009
▪ The timing point of Misdirection's action trigger is: during the other player's action's Required Targeting Step, in between the last required targeting in the constraints block (if any) and the first required targeting in the effects block (if any). Misdirection can be played even if there is no targeting in the constraints block or no targeting in the effects block. [CLARIFICATION, 8 May 2008
This is really confusing my play group. Does this mean you can use Misdirection on Unfamiliar Ground? How would that even work as the card never targets anyone? Who would you change the target to if it doesn't target in the first place? Very confusing.
Zen Faulkes (rules official), 25 March 2009
(Can you use) Misdirection on Unfamiliar Ground?
No. Unfamiliar Ground does not target. Clarification: Misdirection can be played, but it does nothing to the outcome.
The ruling is referring to when Misdirection is played, not what it is played in response to or what it will allow you to change.