magical brainwashing? well.... if magic exist (you did say sci-fi instead of fantasy) then there would be some law in place regarding.
What can magic do? practically anything within our imagination.
edit: gah, press enter too quickly.
Ok. What laws "would" be in place in such a setting?
1. Protection - probably using harmful magic against another person would be prohibited in a society of our scale (i.e. U.S. for example)
2. tracking - is this magic "mana" base? something to think about. How does one know if your mind is magically erase? is it a total wipe? only wipe a certain event? does it leave traces of magic or alteration? can it be detected? (is it a mystery story?)
3. punishment - what kind of punishment would there be if such an act is done?
4. Can it be undone? it is magic after all
Laws
what level of severity would this be consider?
A mind is a private place so breaking and entering comes to mind (pun intended)
damage to personal property (you can consider memory is personal property)
invasion of privacy (are there mind readers in your story? that will be a whole new sets of laws)
is there magical protection FROM such mind altering spells/devices (Magneto comes to mind) is there is then you have "intent on harm" instead of possible "magical misfire"
motive? - premeditated crimes have harsher punishment
Torture? - is the process painful?
Cruel and unusual punishment? was the brain wipe sanction by a government entity?
these are just examples (I had thought of something similar story more like a murder mystery but never took off)