Dunstan alleged the defendants - consisting of senior public servants and the Commonwealth - had colluded in an unlawful campaign to have him terminated from the public service.

But the ACT Supreme Court threw out Dunstan's case, finding his claims were statute barred and unfounded.

A judgment on the case, published on Wednesday, said Dunstan had been assistant director of the Australian Taxation Office's database administration subsection in 1990 when a soured office romance led to complaints and counter-claims of alleged workplace conduct.

Dunstan, who had been dissatisfied with management's response, launched various proceedings against his work colleagues.

About June 1997, the ATO launched an investigation into suspicions Dunstan had conducted system violations of the department's mainframes.

The probe found evidence Dunstan had committed the violations, which could have had potentially serious consequences for the ATO at the time.

He was immediately suspended and escorted from the office, and, in October, was told he was under investigation for two charges of misconduct and was suspended without pay.

But in December 1998, before the charges could be determined, Dunstan posted 28 explosive devices to senior officers of the ATO in Canberra and Sydney.

A postal worker was injured when one blew up at Canberra mail centre, in Fyshwick. The others were intercepted by the police.

In 2000, Dunstan was convicted on charges of posting an explosive and attempting to inflict grievous bodily harm, and sentenced to 11 years' jail.

He spent nine years behind bars.

Dunstan was sacked from the public service in 2001, about a year after he was imprisoned.

In 2009, Dunstan discovered a minute from the ATO probe, and claimed it was a decision not to charge him with misconduct.

He claimed the defendants then conspired to overturn that decision and have him unlawfully sacked.

Dunstan alleged the Commonwealth and its employees at the tax office had acted so as to commit misfeasance in public office, breach of contract, conspiracy, defamation, and interference with contractual relations.

But Justice John Burns said he had been satisfied the defendants' actions had been part of "legitimate management discussions within the ATO, and were not part of a conspiracy to harm [Dunstan]".

The judge was satisfied that the defendants did not attempt to have Dunstan sacked outside of the scope of the Public Service Act, and did not act in bad faith in their dealings with him.

"There is no evidence to suggest that this discussion about potential means of dealing with the issues created by the plaintiff in the workplace was contrary to law or the practices of the public service," Justice Burns wrote in his decision.

"Only the most jaundiced eye could see in this correspondence evidence of a conspiracy against the plaintiff.

"Whatever may have been the rights or wrongs of the plaintiff's complaints about his workplace or his colleagues, it was indisputable that his actions had consequences within the section in which he was working, and that management had to deal with those issues."