I read it several years ago but I have no idea when it was published.
What I remember is that some people are born with a magical talent and some people are born with the ability to take that talent from others by killing them.
The protagonist's son has an ability and the protagonist goes to an old woman who has the power to remove (and presumably destroy) the gift in people; she gets ticked at him and throws him out.
His son uses his ability in a crowded tavern and is seen by one of the people who can take powers. A chase and battle ensue and the father kills the power taker. When the taker dies the father sees the souls of his victims leaving and realizes he could reach out and take the powers for himself.
he goes back to the old lady and she has him kill her and take the power to destroy the gifts in others