A revealed Boastful Proclamation and avoided the destruction of the province. The honor gain from this would get him to 40 honor.
Does he win the game at that point, or his honor total is checked before the honor gain happens?
Boastful Proclamation and Honor win timing
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 revealed Boastful Proclamation and avoided the destruction of the province. The honor gain from this would get him to 40 honor.
Does he win the game at that point, or his honor total is checked before the honor gain happens?
As of the most recent printing of this card (Khan's Defiance) the timing on the honor gain and the check for an honor win are simultaneous; and since they are both triggered effects resolving at step B of the timing sequence, the active player chooses which resolves first.
Please note that this ruling is based on CE timing and an older card printing; its interaction in Emperor Edition may change.