I'd say that it might be a case by case thing based on the source of the sponsored magic and if the lawbreaking was at the request/desire of the sponsor (I'm assuming first law).
In Changes Lea tells harry something about the complexities f extracting payment due:
Specifically that he helped her extract payment due to her to balance the scales of her exchange of Michael's sword for the dagger.
I'd probably rule differently on killing a first law violation* to balance the scales of debt between the sponsor & victim, than one committed against a doorguard, even if in the process of balancing scales with a third party employing the mook. I'd definately rule differently if the victim was just some mook/villan unrelated or indebted to the sponsor.
* even moreso if other reasonable avenues had been first attempted unsuccessfully & I painted them into a corner.
Can you give any details about the hypothetical situation
Yeah I realized I may be asking the wrong question here. I am starting to think the right question is can no caster talent mortals outside of the knights be imbued with Seelie or Unseelie magic?
The knights seem to be a special case as they have their own "mantle of power" they gain when they take up the role that seems to have a lot of power wrapped up in it. So it seems to me that it would take a huge investment from ether court to imbue a normal mortal with Fairy Magic.
Can anyone think of examples in the books that would support a total non practitioner getting any sort of powers imbued into them? The closest I can think of is from changes Susan getting the super outfit in Changes and even the that's not really her getting powered up so much as her stuff is getting temporarily enchanted
So maybe to wield Fairy Magic you must be some sort of practitioner no matter how small and thus are subject to the laws if not a changeling, Knight, or Fairy.
Thoughts?