It is legal (if morally bankrupt and unethical) for the people at FOX NEWS (TM) to lie, distort, cheat, and make up any shit they want and claim it is true, because of a 2003 Florida court ruling.
In other words, because no fool ever thought "Well, we'd better make it a clear rule or law, and not just a suggestion, that lying on television is wrong, or you just know someone from that profession of people who cherish their reputations for honesty will start lying all over the place, and make a business model and power grab out of it."
Note, this isn't the same thing as "having fought a legal battle for the right to lie." Alas, while quite believable, that is just an urban legend.
However, as I said, the cited court case firmly cemented the legality of lying as totally legal. Journalism as a professional has a sense of ethics, and proper conduct, but there are no laws requiring people who call themselves "journalists" to tell the truth, any part of the truth, or even to not completely invent shit on the fly.
So, yeah, pathological liars like Rush Limbaugh and Bill O'Reilly can actually call themselves journalists, and no one can stop them. Well, that is unless we can embrace their own mantra of "free market" and convince advertisers to pull the plug. Which, actually, given the false adherence to any kind of principle of their leash-holding masters, Rush's program has been on life-support for years. Yep, his program has been dying a slow death in many markets, but the people who own those radio stations keep airing his program, despite lack of sponsors, despite dead air time. "Free market" should say his program got cut years ago, but the plug hasn't been pulled, because the people who use him as their whipping boy are hoping to win the war of attrition by keeping him on the air.