Walter Sofronoff KC has asked the Federal Court to toss out the ACT corruption watchdog's findings delivered in March, stemming from leaks to a journalist.
But the watchdog on Tuesday said its report may be protected by parliamentary privilege.
"It raises the question of whether these proceedings should take place at all," Scott Robertson SC, for the ACT Integrity Commission, told the court.
Parliamentary privilege is designed to allow parliament to go about its business without outside interference, such as from the courts.
The commission is overseen by a parliamentary committee but its report has also been published online.
The speaker of the ACT parliament, Liberal Mark Parton, was also seeking to be involved in the case.
But Adam Pomerenke KC, for Mr Sofronoff, suggested that would only duplicate what the commission would say.
The case is due to return to court in July.
Mr Sofronoff, a former Queensland Supreme Court judge, chaired a board of inquiry into the ACT's criminal justice system after controversy plagued the prosecution of Lehrmann, accused of raping his then-colleague Brittany Higgins in the ministerial office of Senator Linda Reynolds at Parliament House in 2019.
A 2022 criminal trial was abandoned with no verdict because of juror misconduct.
While prosecutors opted not to hold a re-trial, their public statements and treatment of witnesses was put under the microscope by the Sofronoff inquiry.
It found the territory's top prosecutor Shane Drumgold had lost objectivity over the case and had knowingly lied about a note of his meeting with broadcaster Lisa Wilkinson.
Mr Drumgold resigned and launched a legal challenge in the ACT Supreme Court.
It found the majority of the inquiry's findings were not legally unreasonable, but it struck down an adverse finding about how Mr Drumgold cross-examined Liberal senator Linda Reynolds during the Lehrmann trial.
The judge also ruled Mr Sofronoff's behaviour during the inquiry gave rise to a reasonable apprehension of bias and he might have been influenced by the publicly expressed views of a journalist.
Mr Sofronoff repeatedly messaged with the News Corp journalist and eventually leaked her an advance copy of his probe's final report.
That leak led to the integrity commission's "serious corrupt conduct finding" in March.
1800 RESPECT (1800 737 732)
National Sexual Abuse and Redress Support Service 1800 211 028
19°C