A public servant sacked for anonymously tweeting her private views about Australia's immigration policies will front the High Court today in a battle over whether public servants have the right to freedom of political speech — and lawyers say the case's implications could be wide-reaching.

Key points: Government says social media guidelines maintain the apolitical nature of the public service

Government says social media guidelines maintain the apolitical nature of the public service Michaela Banerji says guidelines did not apply to her comments, which were anonymous

Michaela Banerji says guidelines did not apply to her comments, which were anonymous Workplace lawyer says case could clarify rules over the line between work and personal time

Michaela Banerji worked for the Department of Immigration and Border Protection from 2006 to 2013, when her employment was terminated after it was discovered she was behind a series of tweets highly critical of the government.

She had posted more than 9,000 tweets under the Twitter handle LaLegale, which she still uses.

At the time her tweets, which covered topics from "our invasion of Iraq" to offshore processing, were anonymous, did not disclose confidential information, and were posted outside work on her personal phone.

She only tweeted once while at work.

Ms Banerji won a case in the Administrative Appeals Tribunal, which has been appealed to the High Court. ( ABC News )

Court documents reveal some of the drama played out on Twitter when her boss Sandi Logan tweeted back at her saying: "Give it a rest @LaLegale. #DIAC celebrates success, not mired in harping. If you have a policy frustration, take it where it will make a diff."

Ms Banerji retweeted another Twitter user who said "@SandiHLogan What a rude response! And where would you suggest @LaLegale take her 'policy frustration'?"

She was eventually unmasked and sacked after an investigation found she had not upheld public service values, by not adhering to guidelines on the use of social media and making public comments, even in an unofficial capacity.

Ms Banerji later suffered post traumatic stress from her sacking, and was awarded compensation by the Administrative Appeals Tribunal (AAT).

The Tribunal found her sacking was not lawful, and that the Public Service Act was at odds with the implied right to freedom of political communication in the constitution.

Important case for all employers

Now the Federal Government wants to overturn the AAT ruling in a test of whether public servants have the right to freedom of political communication.

To determine the answer the court must consider the question in two steps.

The first is to determine if the implied right to freedom of political communication in the constitution is compromised by the law.

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Even if it is, the law can still be valid, under the second step which asks whether it serves a legitimate purpose compatible with the maintenance of representative and responsible government.

The government says in its submissions this is exactly what the Public Service Act does.

"The history of the relevant provisions demonstrates that they have long been regarded as performing a central role in preserving the apolitical nature of the [Australian Public Service], which is in turn essential to its capacity to perform its role exercising executive power."

But Ms Banerji will argue the guidelines do not apply to her case.

"These provisions do not apply to 'anonymous communications' in the sense of communications whose immediate context evinces no connection to the speaker's status an an … employee."

Workplace Relations Lawyer James Mattson said Ms Banerji's case had implications for all employers.

"What previous hearings on this topic have grappled with is the increasingly blurred boundaries between your work and personal time," he said.

"If an employee posts anonymous comments on social media, can an employer who later finds out the identity of the employee, use these posts as grounds for dismissal?

"Secondly, is an employment contract or policy that requires a worker to behave 'at all times', in regard to their employer's interests, appropriate and legitimate?"