Hm. You know, I think I've been looking at mental damage in the wrong way. I've been seeing it as sort of amind blast type of a thing -- like punching, but mentally -- which would, therefore be great for things like knocking people out without physical trauma. Reading through YS more carefully, I think I'm agreeing with mostlyawake. Mental conflicts are about attacking the target's thought processes, and inflicting consequences that represent a forced change in their mental processes. As such, then all use of magic for mental attacks would be basically a variation on the theme of mind control, and would be a violation when used on people.
It looks as though what I thought of as a mental attack -- the magical sucker-punch to the cranium, thus knocking them out -- would still be a physical attack, doing physical stress, with physical consequences (like "Whanging headache" or "Stunned" or "Concussed" instead of "Profuse Bleeding" or "Broken Leg", but still physical consequences nonetheless).
Hm.
Then again, wouldn't illusions count as a mental maneuver, resulting in an aspect along the lines of "I see purple elephants!"? And the discussion of Harry's love potion makes it sound as though there is some grey area where certain mental manipulation is too minor to count as "enthrallment".
Ok, I thought the mist was clearing, but perhaps not. :p
An illusion is a smoke and mirror (ok, magic light) show that creates an EXTERNAL effect, and is detected by a sensory organ (eyes, ears, ect), which is then translated into thought internally. Thus, it remains physical, and is defeated (most likely) by a high physical roll (alertness, modified by lore, perhaps).
Putting a thought into your enemy's head (making ONE person hear voices, perhaps, and doing so internally instead of just creating a whisper by their ear) is probably 3rd law? (never invade the mind of another), if not it's clearly 4th law (mentally tampering with them to change their behavior).
For that matter, rendering someone blind is physical (although still lawbreaking possibly, as it's transformation. Shooting their eyes out with fire = fine; making a spell that just makes them blind might be lawbreaking) but making a spell that leaves their eyes intact but makes them not understand the data received is mental lawbreaking.
Weird, huh?
Creating a bubble of darkness around their head that moves with them is the safest bet, but if you then kill them, you just used magic to help you do so... lawbreaker!
Screw it. Buy a gun.