Law is meant to deter people from breaking it. It's never going to get 100% of everyone. Fake news needs to be rated fake by isps, or content providers, something. There needs to be a reputable source of validation for media. We just let that all go. Journalism has no integrity now. And it doesn't seem there is a demand for it.
But banning or fining, by a government body, will clearly be fertile ground for bias to develop.
Maybe, the same way it's illegal to yell fire... it should be the same way for clearly fake news. I just worry putting Republicans ahead of the board of what is fake or not.. in this world, I'd imagine states denying information about the flint water crisis for example. As they'd need to be verified by some system or form of government.