The federal government is appealing a ruling that found an Immigration Department worker was unlawfully sacked for tweets critical of asylum seeker policies.
Federal workplace insurer Comcare lodged the appeal on Monday, setting the scene for a fight in the Federal Court over the appeals tribunal's decision for Michaela Banerji to receive compensation.
The Administrative Appeals Tribunal decision redirected scrutiny to the Immigration Department's dismissal of Ms Banerji for tweeting criticisms of detention policies, and challenged Australian Public Service rules stopping public servants from expressing their political views on social media.
Ms Banerji took the government to the tribunal after federal workplace insurer Comcare refused to compensate her for the psychological condition that developed after she was sacked in 2013 over tweets from a pseudonymous Twitter account.
The tribunal overturned Comcare's decision and found she suffered depression and anxiety that could be classed an injury under federal compensation laws.
Ms Banerji was working in the Immigration Department when co-workers learnt she was behind the tweets railing against the government's treatment of asylum seekers.
She 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".
The tribunal said Comcare's refusal was based on a dismissal that was unlawful because it intruded on her right to free political expression.
Her tweets, made from the Twitter handle @LaLegale, were anonymous and did not disclose confidential departmental information, but an internal investigation in 2012 found she had breached the code of conduct for government employees.
In a submission to the tribunal, her lawyer, Allan Anforth from Canberra Chambers, said the tweets had been posted from her own phone and, in most cases, outside work hours.
The tribunal described government efforts to restrict anonymous comments from its employees as Orwellian.
It lashed the decision to sack her, saying it "impermissibly trespassed upon her implied freedom of political communication", and "with a law only weakly and imperfectly serving a legitimate public interest".
The Federal Court is yet to set a hearing date for the appeal.