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.
Does the kill action on Swift Punishment require that the target be opposing your magistrate? As worded, it does not appear to.
Swift Punishment
Battle: Target one of your unbowed Magistrate Personalities: Take the Imperial Favor. If he was targeted by Passing Judgment this turn, you may destroy a target Personality with Personal Honor lower than your Magistrate's Chi.
Thanks
Does the kill action on Swift Punishment require that the target be opposing your magistrate?
No, but he must be at the current battlefield, per the Rule of Location: "Any cards in units must be at the current battlefield to be legally targeted by a Battle action."
Swift Punishment's Battle action targets your unbowed Magistrate Personality and it may target a Personality with Personal Honor lower than your Magistrate's Chi, and Personalities are always cards in units, therefore both targeted Personalities must be at the current battlefield but they may be in the same army.