Although spirit warriors employ magical abilities, they are not mages; instead, they flirt with inhabitants of the Fade who agree to augment mortal abilities in exchange for a glimpse of the physical world. Naturally, the Chantry's templars rarely acknowledge that distinction.
You can use the ability Fade Burst to kill city guards in Amaranthine (At least the one who is with another guard in front of the gates)
Oghren and Brogan Dace can learn this specialization despite being dwarves, suggesting that dwarves may not be completely cut off from the Fade and showing another form of a spirit's magic affecting non-mage individuals as is seen in the Broken Circle quest.
Fenris in Dragon Age II, while not strictly a spirit warrior, boasts many similar abilities and follows the same principle of a warrior wielding magical energies.