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, 30 January 2010
http://www.l5rsearch.com/db/search.cgi?cmd=detail&card_id=8189 Hida's Guidance Crab Clan players' provinces have +2 strength.
http://www.l5rsearch.com/db/search.cgi?title=Determined%20Force Determined Force Battle: Set this battlefield's province's strength equal to its base strength.
My opponent is Crab and has Hida's guidance in play. We are at a battle at one of his provinces If I play determined force for its first action - what happens? a The province strength is reduced to printed for the remainder of the turn or b The province strength is reduced to printed for an instant, then the Hida's Guidance trait re applies and province strength = Printed + 2
Many thanks
Brook Cunningham (rules official), 30 January 2010
My opponent is Crab and has Hida's guidance in play. We are at a battle at one of his provinces If I play determined force for its first action - what happens? a The province strength is reduced to printed for the remainder of the turn or b The province strength is reduced to printed for an instant, then the Hida's Guidance trait re applies and province strength = Printed + 2
The answer is "a".
The setting of the province's strength to its base has no stated duration, so it lasts until the end of the turn. Like a stat bonus that comes under a subsequent penalty, contiuous effects like Hida's Guidance's won't try to "re-apply".