Mr Roberts-Smith is suing three journalists at Nine newspapers over published allegations he committed war crimes in Afghanistan between 2009 and 2012.

He vehemently denies any wrongdoing while serving in Afghanistan with the Special Air Service Regiment.

Justice Anthony Besanko had listed the Federal Court trial to start on June 15, with six weeks set aside.

On Friday, he published his reasons for vacating the trial and adjourned the matter to a case management hearing on May 14.

The judge heard submissions in April about whether the trial should be delayed, after noting the escalation of the COVID-19 pandemic as well as issues relating to the detailing of national security information.

Mr Roberts-Smith's barrister had argued it was premature for the court to conclude it wasn't feasible to go ahead with the trial in mid-June.

"He reminded me that the imputations said to arise from the matters complained of are very serious," the judge said.

Evidence was given by his solicitor of the ongoing impacts on Mr Roberts-Smith and his family by the respondents repeating at least part of the allegations every few months.

After a 60 Minutes broadcast and subsequent articles by the respondents in September 2019, one of his children was told by another student that "Your dad's a murderer", the solicitor said.

Another incident involved a car pulling up next to him, the driver pointing his fingers in a gun shape at him and making shooting sounds.

He also had no public speaking requests, whether paid or voluntary.

He previously always received numerous invitations to attend ANZAC Day services or events.

"Despite being Australia's most decorated soldier, the applicant, during the period prior to the cancellation of ANZAC Day events this year, did not receive any requests to attend any ANZAC Day services or events for ANZAC Day 2020," the judge said, citing the solicitor.

He ruled that an in-person trial, rather than a virtual hearing or part-hearing, was necessary to deal with the issues relating to the disclosure of national security information.

"The second reason is that this is a trial where the credibility or reliability of the key witnesses may well be crucial in circumstances where the alleged imputations arising from the matters complained of are, as I have said, very serious indeed."

But an in-person trial starting on June 15 would not be possible, given the current social distancing requirements.

"Just as important are the travel restrictions and self-isolation requirements associated therewith in a case where there are potentially a large number of witnesses from outside New South Wales and some from outside Australia."

Australian Associated Press