According to Anita Blake, ghosts cannot actually harm a living person, but paying attention to them allows them to become more solid and attempt to harass or scare their victims. Anita generally tries to avoid animating a corpse if the deceased person's ghost is still haunting their grave. She appears to have no power over them, either, as ghosts are a type of "soul magic," as noted in The Laughing Corpse. As yet, no clear information on their legal status in the Anitaverse has been revealed.
The master vampire Seraphina had the power to summon and control ghosts, similar to the more common vampiric power of calling particular animals.