The nation's highest court has found the federal government's limits on free speech in the public service are constitutional, in a decision that clears the way for punishments targeting bureaucrats who express political views.
High Court judges handed down the decision on Wednesday after a six-year legal battle over the Immigration Department's dismissal of ex-public affairs officer Michaela Banerji for tweets critical of the government.
Attorney-General Christian Porter last year applied for the court to hear the case after an appeals tribunal sided with Ms Banerji when she sought compensation for post-traumatic stress following her 2013 sacking.
High Court judges overturned the tribunal's decision and found that restrictions on public servant free speech were consistent with the constitution's role maintaining an apolitical public service.
Laws limiting freedom of expression in the bureaucracy were "reasonably appropriate" and in proportion to their purpose, judges said.
The finding vindicates the federal government in its restriction of free speech for public servants, confirming laws stopping bureaucrats from expressing political opinions do not contradict freedom of speech implied in the constitution.
This is a really naive decision in terms of the political realities that exist in the community.- Lawyer Allan Anforth
The court also found the implied freedom of political communication in the constitution was not the same as a personal right to free speech.
"Even if a law significantly restricts the ability of an individual or a group of persons to engage in political communication, the law will not infringe the implied freedom of political communication unless it has a material unjustified effect on political communication as a whole," it said.
The decision also found that tweeting anonymously was no protection, as it could be expected that someone's identity would be revealed.
Speaking outside the court, Ms Banerji said the decision was a loss for all public servants.
"The only advantage of taking this action was to affirm the role of freedom of speech for public servants. And we've failed," she said.
"It's not just a loss for me, it's a loss for all of us, and I'm very, very, very sorry."
Ms Banerji's lawyer Allan Anforth said the decision reflected an outdated view of the federal bureaucracy and its employees.
"This is a really naive decision in terms of the political realities that exist in the community," he said.
The finding would also reach into the private sector and allow its employers to limit the free speech of workers, Mr Anforth said.
"If the employee is critical of the employer's position on some politically relevant, social issue, they can be sacked," he said.
"The logic of it does not stop at the boundary of the public service."
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While the Administrative Appeals Tribunal in 2018 agreed with Ms Banerji that her dismissal intruded on her right to free political expression, federal government lawyers appealed the decision and argued the sacking was reasonable action.
Three state governments joined the Commonwealth's side in the High Court case, supporting the restrictions used to discipline Ms Banerji and defending their own limits on free speech in the bureaucracy.
The court's decision is a win for federal and state governments and will clarify their limits in responding to public, political comments from their staff.
Greg Barns from the Australian Lawyers Alliance said the result showed Australians' free speech wasn't protected.
"This case shows that Australians lack fundamental protections such as freedom of speech. The lack of a national human rights charter means government can shut down dissent far too easily," he said.
Community and Public Sector Union national secretary Nadine Flood labelled the decision disappointing and said it could affect almost two million Australians working across the federal, state and local governments.
"People working in Commonwealth agencies should be allowed normal rights as citizens rather than facing Orwellian censorship because of where they work," she said.
"At the end of the day the government has a responsibility to protect freedom of speech. The Morrison government needs to demonstrate that it prioritises democratic rights, with a social media policy that reflects the real world.
"The notion that the mum of a gay son who happens to work in Centrelink can't like a Facebook post on marriage equality without endangering her job is patently absurd."
Ms Banerji was the author of tweets criticising the government's asylum seeker policies, written from 2012 under a pseudonym LaLegale, before she was detected and later outed by the Immigration Department.
She tweeted in her own time, except on one occasion, and didn't disclose any confidential information.
Lawyers for the federal government, speaking at the High Court in March, defended the limits on political expression that brought on Ms Banerji's dismissal.
Solicitor-General Stephen Donaghue told judges the restrictions protected the bureaucracy's impartial role.
The freedom of speech implied in Australia's constitution accommodated the need for an apolitical public service, making the restrictions constitutional, he said.
Mr Donaghue denied the laws were a blanket prohibition on political communication from bureaucrats, saying they only controlled free speech to the extent it risked the apolitical role of the public service.
The former public servant's lawyers said the public needed to know about the non-confidential workings of the bureaucracy and restrictions to free speech for bureaucrats impeded the flow of this information.
Lawyer Ron Merkel said rules that brought on Ms Banerji's sacking applied too broadly by letting public service employers sanction staff for creating the risk of harm to the bureaucracy's apolitical reputation, in the case they were later identified.
Ms Banerji previously lost a high-profile attempt to stop her dismissal in the Federal Circuit Court in 2013, a decision seen as likely to curtail other bureaucrats' use of social media when judge Warwick Neville found Australians had no "unfettered implied right (or freedom) of political expression".