Directly tampering with the human mind, either by reading it or modifying it, is a direct violation of the Third and Fourth Laws, respectively, no matter how you do it or what your motives are. Both of them are a sure way to have the Council Wardens on your trail in no time. Specifically, it is forbidden to directly use magic on human beings for those purposes.
However, instead of asking how to attack a human's mental stress track without violating the Laws, it would be better to ask how a PC can achieve some end using magic (you mentioned spirit magic and evocation, right?) without violating the Laws. Stress tracks are only a construct of the system, and the focus should be in the narrative.
Depending on what the PC wants to do with his target, there are legal and not-legal ways to do it. Let's see some examples:
Know his secrets: Outright hacking anyone's mind is a task for spirit magic. It is also a violation of the Third Law. But a skilled magician could still learn a great deal about an individual's secrets by using veils and illusions to break into their home unseen and read their mail or personal documents, or to listen in on private conversations with their wife/husband/friend/lawyer/doctor. Some magicians could try to enlist the help of a friendly ghost for that, too.
Make them do what you want: If peeping into another human brain is a big stain of mud on your reputation, then tampering with that same brain's inner workings is like bathing one's reputation in tar. That's another use of spirit magic, and a Fourth Law violation to boot. However, you may still coerce another person, using magic to help you achieve that coercion by mundane means. Blackmail, seduction and outright intimidation work wonders to that end and are completely legal from the perspective of the Laws of Magic. A spirit magician could use the methods described above to get ahold of blackmail material, or he could combine standard stalking, creative use of telekinesis and maybe the services of a collaborating ghost to maintain a subject in a state of fear to make them pliable, as a example.
Just a note. Even if a magician manages to tiptoe around the Laws and avoid a direct violation in this way, repeated use of magic for devious purposes may still attract unwanted attention from Wardens dropping in on your neighbourhood for a visit, just to be sure. Also, while they may not recognize or understand magic, police and other agents of the mundane law may still want a word with you if you are caught doing certain things...