That law doesn't do a good job of discriminating between Establishment Journalists and regular citizens. In fact it obviously does that so badly that I don't think such was even their intent. If anonymous sources do have value (and I doubt I could be convinced otherwise) how did it become in the public interest to permit the government to make a very short, (quite possibly) uniformly biased list of the only people they can safely speak to?

And even if a prestigious reporter gets sued for defamation, I doubt "I have proof from a source I can't reveal" would work as a defense.