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, 5 April 2008
So, with Chag's ability:
Even if Chagatai is bowed or has been in a battle resolution this turn: Move him to the current battlefield. If he is now opposed, straighten him.
Normally, if an attacking personality has been in battle resolution already, he cannot move into another battle. Chag's ability gets around this. So if I used something like Determination to send him home, can he use The Khan to move back, even though he couldn't normally do this without his ability? Or is it that once I send him home, he's stuck there because he can't use his ability again to override this?
Thanks.
Brook Cunningham (rules official), 5 April 2008
...once I send him home, he's stuck there because he can't use his ability again to override this?
Yes, the above quoted part is correct.
The "Even if" clause (see http://rules.l5r.com/Glossary_E#Even_if) is contained within Chagatai's ability, therefor it only affects the legality of that ability.
If Chagatai has already used his ability this turn and has already been attacking in a battle resolution this turn, actions that move him into a battle (like the one on The Khan) do not move him (see here: http://rules.l5r.com/Glossary_M#Move)* unless they also contain such a clause.
*(Fixed and clarified, 4-7-08)