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, 24 March 2009
Since there are no rulebook effects for Formations, what's going to happen with them? If I play a formation there's nothing in the Samurai rules that explicitly say that you get another immediate action after playing them, in fact there's nothing in the rulebook that even states that they stay in play. It would be really neat if someone could make an official announcement on how formations work for Legacy.
For some cards like Broken Shinbone Warren it's fairly obvious how the card should work, but because they don't say "even while bowed" they don't work at all. Is there going to be any clarification for cards like these so that they're more playable under Samurai rules? Thanks.
Brook Cunningham (rules official), 24 March 2009
Since there are no rulebook effects for Formations, what's going to happen with them? If I play a formation there's nothing in the Samurai rules that explicitly say that you get another immediate action after playing them, in fact there's nothing in the rulebook that even states that they stay in play. It would be really neat if someone could make an official announcement on how formations work for Legacy.
For some cards like Broken Shinbone Warren it's fairly obvious how the card should work, but because they don't say "even while bowed" they don't work at all. Is there going to be any clarification for cards like these so that they're more playable under Samurai rules? Thanks.
Apparently, however you came to be informed about the existence of the Legacy Format, your source left out one crucial piece of information.
There are Rules governing that format, found here: Legacy Format Rules.
From the main Rules Wiki page, it's under "Alternate Formats".
As to your specific questions...
Formations: http://rules.l5r.com/Legacy_Format_Changes_to_the_Current_Rulebook#Formation
Broken Shinbone Warren: http://rules.l5r.com/Older_Cards#Abilities_and_actions
I hope this document and these answers help you enjoy your older cards, but still feel free to ask questions here if you find them lacking.