They just now changed how they enforce the rules. Of course they have a legal pretense for their action; everyone has a legal pretense.

These rules have generally not been enforced this broadly because the expectation is that they wouldn't actually stand up to First Amendment scrutiny, should it make it to the Supreme Court. Of course, CBS is at no risk of suing the administration if Paramount wants any chance of buying Warner, so in this case they can restrict as they please.