Wikipedia tells me there is such a thing as criminal libel, although it is rarely prosecuted. But that's beside the point IMO. I omitted that libel generally does not fall under criminal law because IMO the fact that the legal system can be used by private individuals to enforce libel laws makes them a government restriction on free speech.
Not in the US. Or maybe you could link a source you claim to have?
The government does not originate tort claims of libel. It is there to mediate disputes that citizens bring against each other. Because the next best thing is people committing acts of violence against each other.
"Criminal libel is rarely prosecuted but exists on the books in many states, and is constitutionally permitted in circumstances essentially identical to those where civil libel liability is constitutional."
Again, this is really beside the point IMO, as I mentioned before. I only brought it up due to being an unreconstituted pedant, unable to help myself.