Where to look for employees’ legal duties?

The legal obligations owed by employees to their employers have various sources. They may be express, for example from the terms of an employment contract or enterprise bargaining agreement, or implied for example fiduciary duties implied by custom and practice, certain statutes, or perhaps common law or equity doctrines. An employer’s policies and procedures may give rise to obligations upon employees such as policies about conduct in the workplace, use of the employer’s property, social media and appropriate use of work IT facilities. Contracts of employment may incorporate an obligation to comply with policies and procedures to observe these policies by not engaging in conduct which could damage the image and reputation of the employer. Curiously (at least to me) is the question whether an employer’s policies and procedures are incorporated into legally enforceable obligations in the absence of an express provision purporting to do so in a contract of employment. This question has been left open by the High Court of Australia.