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, 26 April 2010
The Good Faith Rule: When an action is announced, the player must be able to target all required targets, meet all conditions of the action, and pay all mandatory costs, to the best of his or her knowledge.
Blind Cards Rule: When a rule or card text needs to know what an action does or will do, it only takes into account the current text of the action. It does not consider any continuous, ongoing or triggered effects that change the action's effects or cause them to fail.
Lets look at Ambush for example: I announce Ambush and target a personality I control that may not assign or move to battlegrounds in order to use actions that may be taken even if I control no units at the battleground. Would that be permitted?
Or Unwavering Assault: As the attacker, could I target a personality that was already in battle resolution this attack phase in order to straighten him, even though his movement would be negated?
A player, 26 April 2010
The Good Faith Rule says if a player can legally announce an action that he wants to take, and tells him to consider the game state. For example you cannot take an action with a cost of moving home your Personality if an effect is preventing his movements.
The Blind Cards Rule says what an action does or will do when a rule or card text needs to know it, and tells it to ignore the game state. For example the exceptions to the rules of Presence or Location allows you to target your Personality at home with a Battle action whose effects would move him to the current battlefield, even if another effect is preventing his movements.
Lets look at Ambush for example: I announce Ambush and target a personality I control that may not assign or move to battlegrounds in order to use actions that may be taken even if I control no units at the battleground. Would that be permitted?
Yes.
You wonder whether you can play Ambush so you need the Good Faith Rule. Will you be able to target all required targets, meet all conditions of the action, and pay all mandatory costs? Ambush has no condition, no mandatory cost and two required targets: your unbowed Personality and another player's unit. If the Personality whom you control who may not assign or move to battlefields is unbowed, then he is a legal target and you can legally play Ambush in good faith.
See also the FAQ : Is an action legal if an effect can't happen? and If one effect is negated, will the others still happen?
Or Unwavering Assault: As the attacker, could I target a personality that was already in battle resolution this attack phase in order to straighten him, even though his movement would be negated?
Yes, for the same reasons.