Like him or hate him, Bill O'Reilly had an interesting take on this issue when interviewed by Glenn Beck.
O'Reilly stated that Fredo has a compelling legal position in that CNN will HAVE to take him back since they were fully aware and even supportive of Fredo with respect to Andrew. It's a very, VERY long stretch to call Fredo any kind of journalist (and he's not), but even CNN knows that it was highly improper for Fredo to report on anything to do with his brother.
CNN should have denied Fredo any reporting whatsoever to do with his brother and THEIR failure to do so gives Fredo a very strong position in a legal sense.
Fredo didn't operate in a vacuum. He had producers, directors, writers, and other staff who were complicit in this entire thing.
I think O'Reilly's on to something here, so don't be surprised if Fredo initiates a lawsuit against CNN. What does he have to lose?