I am lost in the gray area between "at will employment" and binding contracts.

How can an employee determine what a contract is? Is it a contract if a company distributes a 12 page memo titled "Corporate Compliance and Ethics" that clearly articulates what is expected, or not expected, of it's employees?

If the language of the ethics policy reinforces the company's other policies, and express' it's commitment to those policies and the laws applicable to the business, doesn't that create a contract that makes all company policies a contract?

Is a manager breeching a contract by instructing an employee to not comply with company policy?

Can a manager fire an employee for not following the non compliant instructions, and still stand behind the at will employment contract?

I remember something from my business law class about a fiduciary contract; an implied contract that requires both parties to act in good faith. This type of contract seems to override the at will employment contract, and prevent an employer from producing duplicitous propaganda that confuses, and disenfranchises the employees while empowering the middle managers who don't have to comply with any of the company policies.