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.
Relevant text:
"You may equip this spell as an Interrupt."
As I understand it, an Interrupt tells you when it is to be played. Given the very broad wording on Legacy, can it attach as an Interrupt to any action?
If the above is true, can I attach it after my shugenja is targeted by an effect that targets a personality without attachments? If so, what happens?
If the above is true, can I interrupt Tamori Touya's printed action to attach Legacy, then bow Legacy for her action?
Relevant text:
"You may equip this spell as an Interrupt."
As I understand it, an Interrupt tells you when it is to be played. Given the very broad wording on Legacy, can it attach as an Interrupt to any action?
If the above is true, can I attach it after my shugenja is targeted by an effect that targets a personality without attachments? If so, what happens?
If the above is true, can I interrupt Tamori Touya's printed action to attach Legacy, then bow Legacy for her action?
In general, you may Interrupt any action. Many Interrupts will only have an effect if played at a certain time, but they are legal to take regardless. The exception to this is Interrupts that begin with the word If, which have a constraint on when you may take them defined by the If clause.
Interrupts always happen before targeting. You may attach Legacy of Tadaka to Interrupt, say and opponent's Entrenched Position, at which time the shugenja is no longer a legal target for the Entrenched.
Good Faith will allow you to announce Touya's action provided you can attach Legacy as an Interrupt, and then target Legacy with her action.