But did the government he served, or any other recent government, impose the same rules on itself?

Shergold was justifying his request that police investigate the National Indigenous Times, which had revealed a confidential federal government plan to abolish the Aboriginal and Torres Strait Islander Commission. Yet, a year earlier, immigration minister Philip Ruddock was caught on tape revealing to a journalist confidential information about an ATSIC commissioner. Far from being punished for the leak, Ruddock was promoted to attorney-general.

That's just one of the many times that ministers or their staff "sabotaged" democracy with impunity.

In September 2014, for example, Sydney's Daily Telegraph reported that an intelligence review had found security at Parliament House needed strengthening. The information was almost certainly leaked by prime minister Tony Abbott's office, and resulted in a front-page story under the headline "Red alert over plot to attack nation's leaders".

There was no plot: the review identified only potential vulnerabilities. And if security was the government's primary concern, it would have kept the report secret until it fixed the problems. But if its priority was raising the political temperature about terrorism, then leaking the report was guaranteed to generate sensational coverage. Tellingly, neither the government nor the police made any attempt to identify the leak's source.

Or take the raid on the Australian Workers' Union's headquarters in October 2017. The police were on a quest to discover whether the union's donations to GetUp! during Bill Shorten's period as the union's secretary had breached the union's rules. Someone leaked details of the raid to the media, and reporters and camera operators arrived half an hour beforehand to catch the action.

The negative portrayal of a major union (and Shorten) on the evening news would no doubt have pleased the government. But attention shifted almost immediately to the question of who had tipped off the media. Industrial relations minister Michaelia Cash denied five times that she or anyone in her office had anything to do with it. But then her media adviser, David De Garis, whom a BuzzFeed article had outed as the source, admitted to her that he had told the media, and resigned.

A senior Australian Federal Police officer told the Senate that eight people had refused to testify about their role in the leak. The police wanted to talk to Cash and justice minister Michael Keenan. They both refused twice to be interviewed, although they provided written statements. In the face of this intransigence, the police meekly surrendered.

The police have abandoned other investigations, too. Just last month, The Sydney Morning Herald revealed that the AFP had quietly dropped its probe into a leak in February this year, at the height of the controversy over "medevac" - the proposal to transfer asylum seekers who need medical help to mainland Australia.

The article based on the leak, published in The Australian, revealed contents of a Department of Home Affairs report on the legislation's potential effects and included details of ASIO's concerns. Its publication drew an angry response from ASIO director-general Duncan Lewis, who said the newspaper had undermined his organisation.

Labor charged that the government leaked the briefing paper. The police decided not to continue their investigation because the prospect of identifying a suspect was "limited".

Most famously, the AFP made only a half-hearted attempt to trace the source of a leak to News Corp columnist Andrew Bolt. The incident had its origins in 2003, before the Iraq War, when an Office of National Assessments analyst, Andrew Wilkie, resigned in protest against the Howard government's misrepresentation of intelligence findings about weapons of mass destruction.

Wilkie protested in a very public way, but observed all the proper procedures. He first informed the office's head that he was resigning, then walked out the door to give his story exclusively to the Nine Network's Laurie Oakes.

In an apparent attempt to discredit Wilkie, the government leaked a classified report he had prepared about the possible dangers of Iraqi weapons of mass destruction, presumably to suggest that Wilkie believed the weapons existed and to show that the scenario he had envisaged had not eventuated during the successful United States-led push to Baghdad.

Whoever leaked the report clearly committed an offence. A few days before the leak, foreign minister Alexander Downer's office had requested a copy of Wilkie's report from the Office of National Assessments. When questioned about the leak, Downer "prevaricated and blustered", in the words of The Canberra Times's Jack Waterford.

Yet the police investigation failed, even though a senior security official told Waterford that "a cop who couldn't solve this one couldn't find his bum with both his hands".

Treasurer Josh Frydenberg was among Downer's staff members at the time; it would be interesting to hear his recollection of events.