Michaela Banerji, for example, was fired by the Department of Immigration for her anonymous political tweets, while Daniel Starr was dismissed by Centrelink for comments on an online message-board. Although Starr won reinstatement in the Fair Work Commission, Banerji's case went all the way up to the High Court. She ultimately lost. Throughout, the public service has maintained a hard line on social media usage - one agency told its employees to "dob in" colleagues over political comment. What has changed?

The APSC's new guidance, issued last month, is notable for taking a more nuanced approach to this complex issue. It acknowledges that public servants "have rights as citizens of Australia to engage in community life". Equally, the guide emphasises that some obligations on public servants extend beyond working hours and may limit their ability to engage in political discussion. The guidance document, so says the APSC, seeks to "strike a reasonable balance between employees' rights as individuals and their obligations as public servants."

That is a laudable aim. We have long been critics of the public service's approach to political engagement by its employees (indeed one of us acted for the plaintiff in early litigation on these issues almost two decades ago). At times, we have probably sounded like a broken record. But we have never denied that there is a compelling public interest in an impartial public service.

The challenge is striking the right balance; there is an equally compelling public interest in not silencing a considerable proportion of the voting population. It has been our view that, for too long, there was no balance at all - the public service's emphasis was solely on protecting neutrality. Accordingly, the APSC's new approach is to be commended.

As ever, the devil is in the detail: specifically, how the guidance is applied in practice by departments and agencies, away from the rarefied air of the APSC. With that in mind, we have some insight and suggestions for public servants and their managers on implementing the new social media policy.

The starting point for all of this is the APS Code of Conduct. Section 13(11) of the Public Service Act provides that a federal public servant "must at all times behave in a way that upholds: (a) the APS Values and APS Employment Principles; and (b) the integrity and good reputation of the employee's Agency and the APS". Among the APS Values are being "respectful" and "impartial".

The bare words of these provisions suggest that a public servant must behave in a way that upholds the APS's neutrality 24 hours a day, 365 days a year. That would seemingly preclude any political tweeting at all.

Whether "at all times" literally means "at all times" is a surprisingly complex legal question that the High Court ducked in Banerji. However, in that case Justice James Edelman set out "six factors of particular significance to any assessment" of whether or not a public servant's political engagement would cross "a boundary, albeit ill-defined, between acceptable expression of political opinions and unacceptable expression of political opinions". This admits, rightly, that there will be many situations where a public servant can quite properly engage in political discussion on social media.

The APSC has simplified Edelman's approach in its guidance with an emphasis on three risk factors: seniority, nexus with work and nature of expression. We will consider these in turn.

A public servant's seniority will, obviously enough, have a considerable bearing on the likelihood that their conduct could (a) impact public perceptions of the APS, (b) undermine working relationships with government and ministers and (c) negatively influence colleagues. In Starr, for example, the Fair Work Commission identified "a departmental secretary, a policy advisor, a ministerial staff member or a senior diplomat" as among the class whose emphatic criticism of the government of the day might impact public confidence.

Similarly, and again not unreasonably, the closer the connection with a public servant's work area, the more likely their public comments could fall foul of the Code of Conduct. The APSC offer a case study example of an imaginary public servant, Alex, "liking" and "sharing" a meme of a political leader portrayed as a clown. It suggests if Alex was a finance officer in a service delivery agency, and the politician was from a foreign country that Alex has no work-related dealings with, this would be low risk. If the meme depicted Scott Morrison, and Alex was a policy adviser in a department interacting with ministers, this would be moderate risk. If Alex was an SES1 at a "central department that interacts with the Prime Minister's Office", that would be high risk.

Finally, the expression used will have some bearing. The APSC says: "The risk to public confidence is greater the more extreme our behaviour and expression, including the tone and language of our posts." Or, as the prior edition of the guidance said more plainly, "is it nuanced and thoughtful, or blunt and inflammatory?"

While it is uncontroversial that a tweet full of coarse language is more risky than polite policy analysis, there is a limit. The High Court has previously held that "Australian politics has regularly included insult and emotion ... [the Constitution] does not protect only the whispered civilities of intellectual discourse". Quite sensibly, then, the APSC has added in their latest guidance that the expression criterion "does not mean that APS employees must always be positive, polite, or even neutral online - the range of acceptable expression is broad."

These factors overlap and intersect. There are no hard and fast rules or mechanical calculations; as the APSC says, it "will always depend on the circumstances of each case". Considering the two recent cases, Banerji and Starr together provide some indication of how they might work in practice.

Ms Banerji was an APS6 employee - at the lower end of the spectrum of seniority. She was employed as a "public affairs" officer in the Department of Immigration. Her tweets were often on matters directly related to border protection policy. Some of her tweets were, as the Administrative Appeals Tribunal described, "reasonably characterised as intemperate, even vituperative, in mounting personal attacks on government and opposition figures".

Mr Starr, meanwhile, was a "front-line Centrelink officer", who frequently participated in an online message board. Sometimes he commented in a thread about Centrelink, posting a range of positive and negative comments.

Most egregious, from the Department's view, was a post where he labelled waiting times for Austudy payments as "utterly disgraceful", encouraged message board members to complain to their local parliamentarian, and contradicted information posted in the thread by an official Centrelink representative.

On the APSC's new factorial analysis, seniority would indicate low risk for Mr Starr and low to medium risk for Ms Banerji. Both were commenting on issues with a direct nexus to their work area, indicating a high risk. Ms Banerji's expression and tone were high risk, while Mr Starr was low to medium. While of course these assessments are being made after-the-fact, the differences perhaps go some way to explaining the different legal outcomes.

One other noteworthy feature of both cases is that Ms Banerji and Mr Starr commented using pseudonyms and were, therefore, effectively anonymous. While Mr Starr identified as a Centrelink employee, Ms Banerji's Twitter account gave no explicit indication that she was a public servant. The APSC's new guidance says: "While the risk is greater if you identify yourself as an employee of the APS or your agency, it is not eliminated if you don't ... If you are posting anonymously, you should assume that at some point your identity and the nature of your employment may be revealed."

Although this is sensible advice from a pragmatic perspective, we respectfully disagree with the High Court's view that Ms Banerji's anonymity made no material difference. As the Administrative Appeals Tribunal said at an earlier stage of her case, there is quite the irony that it was "the Department itself which dissolved her anonymity."

For managers, the key emphasis in the latest APSC guidance is proportionality. The APSC suggests that in low risk cases it is generally not appropriate for an agency to become involved; in medium risk scenarios it might be advisable to discuss the issues verbally, while only in high risk circumstances could it be proportionate to pursue Code of Conduct proceedings. We would hope, following this guidance, that only the most egregious cases conclude with severe sanctions, such as dismissal.

In implementing this new guidance, managers would do well to remember the words of caution issued by Federal Court judge Paul Finn. "I am mindful," he wrote in 1996, well before Twitter was landing public servants in hot water, "of the caution that should be exercised when any extension is made to the supervision allowed [to] an employer over the private activities of an employee. It needs to be carefully contained and fully justified."