And the writer goes hmmm, what is the legal standard for someone whose powers, however lethal, are intrinsic and can't be turned off?
Probably the Typhoid Mary standard: lock him up. What other choice do you have?
Well, as the author, I have the choice of making the powers something you acquire. Willfully and by choice. With the added power of being pretty immune to other people's love magic -- since being irresistable to women is not much of a power if you proceed to fade away to nothing on your first victim's grave. Then you have no one but yourself to blame if you end up in a cell without human -- err -- elfin contact for the rest of your life.
Especially after you got into a seduction face-off with a mermaid, also capable of seducing and not being seduced, and the consequences were wide-spread.