A person can report a breach of contract, if there actually is one: the risk is that they are mistaken and they make a false claim, in which case they may be sued for defamation. This would almost certainly fall under the rubric of defamation against public figure, where one must show "actual malice" (such as knowing that the claim is false, or having reckless disregard for the truth of the statement).
Another consideration is that a publisher might believe themselves to be open to lawsuit for tortious interference, as in the infamous 1995 case of CBS 60 Minutes backing down on an interview, where they felt that maybe they induced the interviewee to breach a non-disclosure clause in a contract (it is generally held that CBS's concerns were ill-founded).
The only imaginable path for retribution against the employee would be a non-disparagement or non-disclosure clause in the employment contract. "Disparagement" is sufficiently under-defined that telling the truth about a company's actions would not be "disparagement". Non-disclosure clauses are founded on the idea that some employees are entrusted with secret information, and there would be no duty of no-disclosure with respect to a rank-and-file employee reporting a legal wrong-doing by a company.
On the contrary, an employee is generally protected against retaliation for such revelations, owing top various whistleblower protections. The details are state-dependent, here is a state-by-state summary.