The Communications Act of 1934 created the Federal Communications Commission (FCC) and provided the basis for how it works. It is a violation of the Act for broadcast media to knowingly falsify a news report. The FCC may penalize broadcasters for doing so.
However, another important goal of the Act was to protect free speech. So, the FCC must have real proof that the broadcaster lied on purpose before it can take action. An example of this kind of evidence might be sworn testimony from “insiders” with direct personal knowledge of an intentional falsification of the news. That’s a high bar, but Congress’s intention was to make it very hard for the government to intimidate or control broadcasters.