Must be a mistake that Bushi Dojo is legal in Age of Conquest? Oracle says that:
Bushi dojo in Age of Conquest?
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.
Bushi Dojo was reprinted in Honor and Treachery, this arc's Learn to Play set, with Emperor legality.