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, 12 November 2008
Naval Reaction: If you are the Attacker and your current army has more Naval cards than the opposing army, once per battle after engaging, target your Naval Personality: You have the first opportunity to take a Battle action, which must be performed by the targeted Personality or one of his Naval Followers. [Naval ability UPDATED 28 June 2008]
Fortified Fields Region (This card is not Singular.) At this province's battlefields, the Attacker may not take Battle actions before the Defender's first opportunity to take a Battle action or pass.
Determination Dark Virtue Reaction: Before you announce an action, target one of your Samurai: The action can not have its effects negated or have its targeting changed. After the action destroys any Personality, remove him from the game.
Status: Player A has more Naval personalities, attacking Player's B province which has Fortified Fields attached. Player A after engaging plays Determination and declares Naval reaction. Question: Who takes first Battle action? Player A or Player B?
A player, 12 November 2008
Who takes [the] first Battle action? Player A or Player B?
Player B, after Player A passes.
Determination is played before Player A announces the Naval Reaction, therefore the effect that grants to Player A the first opportunity to take a Battle action cannot be negated (e.g. by Cartographers' Recon action's effects). However Player A may not use this opportunity to take a Battle action, because of Fortified Fields, so he must use it to pass. If Player B passes too, the Resolution Segment begins as usual.
A player, 12 November 2008
In reference to this:
If the Naval reaction were declared normally, would Determination allow Player A to announce and play the first action?
A player, 12 November 2008
No. Fortified Fields forbids Player A to take a Battle action before Player B does so. Since Player A may not announce any Battle action, he may not play Determination neither because it is a Reaction played before announcement, which does not happen.
Determination does not allow a player to take an action that is not legal, it prevents the effects of a legally announced action from being negated.
A player, 12 November 2008
Continuing on this.
How does that parse with Sozen's trait?
Doesn't those 2 have the same designator {cannot - may not} which is overcome by Determination?
Furthermore, since both Fortified Fields and Naval refer to the opportunity of Player A and B of taking a Battle action, I believe that Determination enables the Naval Battle action itself.
If Fortified Fields did not have "opportunity" in it's wording, I'd say you are right. However, based on the existence of the word "opportunity" on both cards, I believe that Determination allows Player A to take the 1st Battle action.
Brook Cunningham (rules official), 12 November 2008
Continuing on this.
How does that parse with Sozen's trait?
Doesn't those 2 have the same designator {cannot - may not} which is overcome by Determination?
Cannot =/= May not.
http://rules.l5r.com/Glossary_C#Cannot:
"When found in card text, and when referring to a type of cost or effect (e.g., bowing, Force bonuses), “cannot” (or "can not") means that a certain type of effect or cost is negated whenever it occurs."
http://rules.l5r.com/Glossary_M#May_not:
""May not" means that a player is prohibited from carrying out a procedure that is usually optional - for example, taking an action, assigning a unit, declaring an attack, bringing a Personality into play, or targeting a certain card - even if card effects make that procedure required...
"May not" is not negation."