I think that if any of what you post can be proved, ideally in writing, then the person who wrote the email (and the company, if it can be similarly proved they knew/authorised said communication) would be in a world of pain should, say, a whistleblower err blew the whistle. They’d be in an...
Unless their contracts of employment explicitly (or possibly, implicitly) contain such a clause, or a clause that could reasonably be so construed, I’d say ‘no’. It would be an unusual contract that so provided (unusual, as in I’ve never seen one).
That said, any objecting employee would be...