That would be a government enforced media silence - media silence just means people not talking to the media or the media not reporting on a subject, it doesn't require a direct order from the government to the media to not report on something. Media might create a voluntary silence, where they agree not to report on a subject, or might have a silence pushed on them, like football's "silenzio stampa", where teams will refuse to talk to or interact with the press when they're unhappy with reporting.