It seems that even a pandemic cannot dull the vexing issue of public servants expressing their political views. As much was evident in Victoria last month, with the state's deputy health officer counselled, albeit not sanctioned, for a tweet comparing COVID-19 to the arrival of Captain Cook. As the subsequent vociferous debate highlighted, there is a broad spectrum of views on whether government employees should be able to speak freely.

In mid-May, the authors were due to participate in a conference at the Australian National University convened to consider this exact topic. With that gathering regrettably postponed, now seems an apt time to revisit these issues in the Australian Public Service context. Almost a year on from the High Court's significant decision in Comcare v Banerji, considerable uncertainty remains.

First, a quick refresher. Federal public servants are bound by the APS Code of Conduct, found in the Public Service Act 1999 (Cth). Section 13(11) provides that government employees must, "at all times", uphold "the integrity and good reputation" of their agencies and the APS. They must also, "at all times", uphold the APS Values, one of which is impartiality - "the APS is apolitical". These requirements are supplemented by policies and guidance from the APS commissioner and individual departments.

The constitutional validity of these restrictions has been challenged on several occasions, with mixed results. Most recently, in 2019 the High Court heard the case of Michaela Banerji, an Immigration employee who had been sacked for anonymous tweets that were highly critical of border protection policy. In August she lost.

One of the judges, Justice James Edelman, helpfully articulated various factors that will inform on which side of the "boundary, albeit ill-defined, between acceptable expression of political opinions and unacceptable expression of political opinions" a particular public servant's comments might fall. These include seniority, nexus with work duties, tone ("from vitriolic criticism to objective and informative policy discussion"), intended audience and explicit affiliation with the APS.

While Justice Edelman's guidance is helpful, the blurriness of the line drawn by the APS Code of Conduct and Banerji is problematic. We do not deny that there are some instances where a public servant expressing their political view could be highly detrimental to public confidence in the APS - say, a departmental secretary publicly attacking policy. In such instances, the Code and the Court are right to demarcate a boundary between what is and is not acceptable.

But far more troublesome is the uncertainty that inhibits any speech anywhere near that line. Following Banerji, a public servant would need to have a significant risk tolerance to make political comments in a public or semi-public forum, even where particular remarks fall on the correct side of Justice Edelman's spectrum. A detailed knowledge of constitutional law should not be a prerequisite to public servants engaging in political debate. And even that may not be enough. There is a risk that an overzealous disciplinary officer might take issue with the speech regardless. If a public servant is on the right side of the law, will they have the resources and desire to fight their department to the High Court?

Recognising that restrictions on speech can silence expression far beyond an intended, justifiable remit, American courts have long endorsed a "chilling effect doctrine". This has seen them invalidate laws, even where partial application is defensible, because the vagueness or overreach of the statute risks deterring speech beyond those justified bounds.

The High Court has repeatedly stressed that American free speech jurisprudence is not apposite in Australia - their First Amendment is an explicit personal right, while our implied freedom of political communication is only a limited protection against government action. That may be so. But the chilling effect is just as potent here. Australians are simply not protected from its perils.

Another complex aspect of this topic is the intersection between these restrictions and academic freedom. The APS, as an employer, is placing increased emphasis on advanced higher education. A number of recent agency heads have had PhDs. Across the federal public service, almost 2 per cent of employees hold doctorates (just under 3,000 staff) - double the Australia-wide rate of 1 per cent. The APS even has a program at the ANU, the Sir Roland Wilson Scholarship, whereby high-achieving public servants are paid to study full-time for a PhD.

There is an obvious tension. For PhD scholars who are still bound by the APS Code of Conduct, or doctorate-holding public servants who wish to remain involved in their academic discipline, as many do, participating in academic debate is fraught. Many such public servants study topics that are politically relevant, seeking to improve policymaking through empirical research. That is commendable. But despite their research being explicitly supported by the government (in the case of the scholarship program), their ability to share that knowledge is restricted - out of fear of breaching the APS Code of Conduct.

This predicament brings to mind the words of Justice Paul Finn, who struck down the Code's predecessor for being unconstitutional in a 2003 case. We do not want, he wrote, "a 'dialogue of the deaf' between those who do not know and those who will not or cannot tell".

In this era of unprecedented political and economic turbulence, all Australians should be able to participate in debate about how our country might emerge from the COVID-19 pandemic. The ability of some public servants to directly comment on their area of work might, necessarily, be constrained. But the chilling effect that persists following Banerji extends well beyond those justifiable limitations. That should trouble us all. As the Canadian Supreme Court has observed, public servants should not be "silent members of society." Least of all during this particular moment in history.