Negligence seems to be one of the things that could actually be said happened here and I'd hope is already on the law books that have been established. If it's not it shouldn't be a hard one to write up and define. What the consequences for the act of negligence would vary depending on how severe the harm to someone else or their property would be. But then how do we measure mental scarring? Imprisonment? An inability to use magic for a set amount of time? Restitution to the victims?