The NSW government previously restricted public protests to 20 people or less with police arresting and fining people $1000 in breach of the public health order.

But on Thursday the order was amended to allow "an outdoor protest or demonstration about a governmental or political matter to take place with up to 500 persons" it states on the NSW Health website.

Paddy Gibson, who organised a Black Lives Matter rally in July, was arrested at The Domain in Sydney after hundreds of police officers and some from the public order and riot squad descended upon the event.

"I think this is a significant breakthrough and comes after consistent activist pressure and large-scale civil disobedience," he told AAP.

"After the National Tertiary Union successfully defended a rally in the Supreme Court police now know they can no longer defend in court their attempts to suppress demonstrations."

"There is this unacceptable double standard where 30,000 people attended a football stadium last weekend, many not wearing masks, but at our rallies we took social distancing really seriously."

Solicitor Peter O'Brien has taken on several cases involving protesters and said police had overreacted and been "abundantly almost aggressive" in the manner they upheld COVID laws at protests.

"It has been disturbing to see some of the ways certain police units, for example the public riot squad, respond to protests like the ones at universities against tertiary funding reductions," he told AAP.

"The manner in which they have used COVID laws to quell those protests has been distressing and disproportionate to the associated risks," he said.

He says COVID public orders had been used unfairly and discriminatorily and there needed to be a healthy respect for protesting in a functioning democracy.

Another Black Lives Matter rally has been organised for Monday on the first day of the NSW parliamentary inquiry into deaths in custody and the mass incarceration of Indigenous Australians.

Speakers will include representatives from the Dungay, Chatfield and Reynolds families who all lost loved ones in custody, and state Greens MP David Shoebridge.

Australian Associated Press