It's not legal. It's just also not illegal. In other words, the state has chosen to not taken a stance on it one way or the other. There are no laws requiring it and no laws prohibiting it. The matter is left up to parents.

If you read between the lines on that article I referenced, the wiman was nailed for contempt of court, not for not circumcising. The contempt was tied to refusal to circumcise, but not because it is required by law. It's because she had agreed to previously as part of a signed legally bound parenting agreement and then changed her mind. So it was failure to follow theoufh on a legal agreement, similar to breach of contract.