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.
How does Plains of Resolution interact with force penalties from tokens already in play (i.e. poison tokens)
Plains of Resolution: Region Singular Open: Bow this card: Your target Samurai contributes Force while bowed and will not have his force reduced by other players' cards.
How does Plains of Resolution interact with force penalties from tokens already in play (i.e. poison tokens)
First, effects of tokens are the effects of cards that created them (http://rules.l5r.com/CE_Non-card_physical_game_elements).
Second, tokens are continuous effects (http://rules.l5r.com/CE_Effects#Continuous_effects).
Third, continuous effects are suppressed by a "does not" effect for their duration, and re-assert themselves when the "does not" effect ends (http://rules.l5r.com/CE_Effects#.E2.80. ... s_Negation).
But this says "will not," not "does not." I can't find any rule that says "does not" and "will not" are equivalent, or that "will not" affects past effects. Since "will not" is future tense, that indicates that it only affects future bonuses.