Can a district attorney threaten to prosecute someone for following a legitimate law?

In Wiconsin, Juneau County District Attorney Scott Southworth is doing just that. The legislature recently passed, and the governor signed, a law requiring schools to have comprehensive sex education curricula. This would include instruction on contraceptives and methods of preventing sexually transmitted diseases.

The district attorney has sent schools a letter stating, “If a teacher instructs any student aged 16 or younger how to utilize contraceptives under circumstances where the teacher knows the child is engaging in sexual activity with another child – or even where the ‘natural and probable consequences’ of the teacher’s instruction is to cause that child to engage in sexual intercourse with a child – that teacher can be charged for contributing to the delinquency of a minor.”

Is Southworth’s action a misuse of his prosecutorial power? Can he threaten someone with legal action simply for following another law?

It is worth noting that he also has a religious agenda. He has said, “You shouldn’t have sex before marriage because that’s the Christian perspective. I’m an evangelical.”