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, 4 March 2013
Say Yoritomo Naoto targets a unit with his ability and then that unit uses A Cleansing Breath. Can that unit use it's abilities now?
I think yes because "may not" is a prevention that is preventing the unit from performing it's abilities and A Cleansing Breath negates "Negate other players' cards' effects that prevent him assigning, moving or performing actions." (emphasis mine)
on a similar not I know that Incense Mill will not negate Naoto but A Cleansing Breath uses different wording than Incense Mill.
A player, 4 March 2013
Naoto forbids using abilities, that's not the same as forbiding to perform actions. A Cleansing Breath will not give you your abilities back.
This is esentially the same question than Incense Mill Vs Soshi Yoshihara XP, and I'm probably missing some others in my search. Cards that prevent "not perform" effects (Incense Mill, A Cleansing Breath) are meant to counter Daigotsu Hotako XP3 and similars, not "may not use abilities" such as Doji Hakuseki XP2 and similars.