In a rare Sunday decision, the NSW Supreme Court sided with police that the risk of community transmission in Sydney made Tuesday's planned event for about 1000 too risky.

Justice Mark Ierace acknowledged there was no evidence a far-larger rally on June 6 - attended by at least 10,000 - had resulted in any transmission of the virus.

But the expert health evidence had since been elevated to "medium" due to multiple clusters in Sydney and the resurgence of the virus in Victoria, he said.

"That current assessment of the level of risk, in spite of relatively low numbers of community transmission, is consistent with NSW presently being on the knife-edge of a further escalation in community transmission," Justice Ierace said, in written reasons.

He found the protest's lunchtime CBD location "particularly concerning" as large numbers of pedestrians not associated with the protest would move through the area and would not be leaving contact details.

Organisers have nevertheless promised to risk arrest and rally as planned on Tuesday before delivering to parliament a petition signed by 90,000 people calling for justice for Indigenous man David Dungay Jr.

Mr Dungay, a diabetic, died after prison officers stormed his Sydney jail cell in 2015 to stop him eating biscuits.

Seconds after the judge announced his orders, a lawyer for rally organiser Paddy Gibson asked they be temporarily suspended to allow for an appeal to be lodged with the Court of Appeal.

The court was told on Friday Mr Gibson had threatened to take the matter all the way to the High Court.

Mr Gibson produced a COVID safety plan, in which he said people should wear masks, practice hand hygiene and leave contact details with organisers so they could be notified in the event a demonstrator tests positive to coronavirus.

He argued protesting was a fundamental tenet of democracy and must be accommodated.

Mr Dungay's nephew, Paul Silva, said his family was disappointed in Sunday's outcome and vowed to keep fighting until there was justice for his uncle's death.

"The police say they want to shut us down because they are concerned about peoples' lives but they don't care about black lives, are we not humans too?" he said in a statement.

In making his decision, the judge accepted there was a risk the campaign would lose momentum if public demonstrations in support of the "Black Lives Matter" movement, in the Australian context, do not continue to be held.

But Justice Ierace said balancing the rights to free speech and protest against the safety of the community at large "at this particular phase of the pandemic" necessitated a prohibition.

The judge also rejected the argument that comments in the media by NSW Police Commissioner Mick Fuller had invalidated or introduced bias into the legal process.

He accepted the evidence of Acting Assistant Commissioner Stacey Maloney that her decision last Monday to take the matter to court wasn't influenced by her boss's earlier comments to radio station 2GB and Sky News.

Mr Fuller had said he'd instructed a subordinate to take the matter to court.

Justice Ierace said it was "regrettable" Mr Fuller appeared to be unaware of the exact legal process for prohibiting public assemblies.

Despite suggesting otherwise on 2GB, there was no evidence Mr Fuller played any role in the decision to take the matter to court, the judge said.

The matter is expected to head to the Court of Appeal on Monday.

Australian Associated Press