dragonlady writes:
I read the article again, and it does NOT say that a parent
eavesdropping on their child is illegal. The mother in question has not
been charged with any crime.

I thought this as well, but I went to news.google.com and
searched for "Dixon Christensen" to get more info about the
case, and apparently in fact the court did rule that it was
against the law for the mother to eavesdrop on her child's
conversations.