"If people are employed, particularly in sensitive areas, and they think that they can go off and be sneaky and cute leaking information or publishing information, or tweeting, whatever it might be, it's unacceptable, and we've been very clear about that," Mr Dutton told Melbourne radio.

The High Court decision has sent public servants into a tailspin, uncertain where the line will now be drawn between what they can and cannot say publicly.

The court found the public service was within its rights to fire Michaela Banerji, a former official in the immigration department who maintained a tweet stream critical of government immigration policy under a pseudonym in 2012.

The High Court found that laws limiting free speech in the bureaucracy were constitutional.

Mr Dutton said the finding showed nobody was above the law. Public servants worked for the government of the day.

"We're not going to have people who are involved in running political campaigns whilst they're employed by the Australian taxpayer, campaigns against the government of the day," he said.

The High Court finding has not only worried public servants, it has galvanised the legal world with debates about what the High Court ruling might mean for free speech.

It has confused free speech advocates who are arguing strongly for Israel Folau's right to tweet his trenchant disapproval of gays. And it has become caught up with the debate about how far employment contracts should reach into people's lives outside work.

Scott Morrison in Public Service Minister but his office said on Thursday he was tied up in Queensland so couldn't comment.

Labor public service spokeswoman Katy Gallagher said the government should provide clarity to public servants as soon as possible.

"Labor will be carefully considering its implications both for the rights of public servants to take part in the political process and express their political opinions, and for the wider Australian community," she said.

"I know that public servants, following the decision, will be worried about the impact this judgment may have on their rights and in particular on the way they can use social media."

Liberal senator and free speech advocate James Paterson said while he had argued against employers trying to control what their staff said on social media, the Banerji case was different.

"There are some areas where it should be permissible for an employer to restrict what an employee can say on social media, and that is where it is directly relevant to their employment," he said.

Ms Banerji had not been "merely critical of government policy", but specifically critical of the department.

READ MORE:

"There is not an employer in the country who would be happy with their employees publicly disparaging them on social media," Senator Paterson said, speaking on ABC radio.

"Ms Banerji should be absolutely free to criticise government policies in areas that are not directly relevant to her employment. Had her 9000 tweets been about climate change policy and her views on that I think that it would have been unfair and unjustified to sack her.

"But given that they were directly relevant to her personal employment with the public service I think that puts it in a different category."

He rejected the suggestion that the Banerji and Folau cases were comparable.

"If, for example, Israel Folau had instead been criticising Rugby Australia saying "rugby's a boring sport, don't watch it, it's run badly by bad people", then I think Rugby Australia would be on stronger grounds to sack him," he said.

"But in this instance, they have sacked him for his unrelated religious views to his role as a sportsperson."

But constitutional lawyer George Williams said the ruling had left public servants unsafe even when they were criticising other areas of government, and would have a chilling effect.

"People will be very wary after this decision for good reason. It does demonstrate the very significant power at the disposal of the government to prevent criticism even anonymously," he said.

The ruling showed that free-speech protections were very limited.

Greens public sector spokesperson Adam Bandt said the ruling threatened public servants' ability to participate in modern life.

"Australian public servants deserve normal rights as citizens, instead of draconian social media guidelines that limit freedom of speech and don't allow for any diversity of opinion," he said.

Professor of constitutional law Anne Twomey said the judgement had not been helpful in distinguishing between different types of political comment among public servants.

While it was legitimate to limit the political communication of executive level public servants, who dealt with ministers, there was no risk of bringing the public service into disrepute if a more junior public servant commented about an issue not related to their work - say a Centrelink employee commenting on climate change or religious freedom, she said.

"It's quite clear the High Court's not going to be sorting this out for the government so it's up to the government to consider what effect its code of conduct has," she said, pointing to the frequent proclamations from the government about allowing freedom of speech in the workplace, including in universities.

Meantime, workplace lawyer Josh Bornstein said opponents of Israel Folau who argued it was a simple breach of his employment contract could not have it both ways.

Contracts now heavily favoured the interests of employers, requiring workers to abide by company codes of conduct and "values". The codes bound workers but not the company itself, he said, writing on the ABC website.

The clauses were "typically couched in admirable language about integrity, decency, inclusiveness and respect", but sought to regulate people's behaviour after-hours.

"In this era of gig work and Instagram, we have become unwitting brand ambassadors for our employers on a 24/7 basis," Mr Bornstein, a principal lawyer at Maurice Blackburn, said. "If we say or do something controversial after hours, and it's disseminated online, we can be fired ..

"Employment contracts and the dark arts of brand management are being selectively deployed to suppress participation in the democratic process."

While progressive concern about Folau's anti-gay tweets was understandable, those who were "cheering on the loss of Folau's livelihood and career have undermined the cause of countless other employees who espouse controversial progressive views and suffer the same fate".

And while conservatives had argued for free speech in the case of Folau, they had shown themselves quick to jettison those principles "at the first sign of views they disagree with".

READ MORE: