Refugee advocates have decided to ride the coat-tails of the Black Lives Matter crew with their own mass protest this Saturday - but NSW Police will take legal action in the Supreme Court on Thursday to stop it.

Activist organisation Refugee Action Coalition Sydney is planning a demonstration on Saturday afternoon at the Sydney Town Hall - the same venue as last weekend's mass rally - to "free the refugees".

At least 1200 people have already said they plan to attend.

Because event organisers lodged the required forms before the seven-day notice period, Police Commissioner Mick Fuller now has to apply to the court to prohibit the assembly.

"The NSW Police Force has received a Form 1 within the required seven-day notice period for a protest planned for Saturday 13 June 2020 at Town Hall," a police spokeswoman said.

"Authorisation will not be given for this protest, and the Commissioner will apply to the NSW Supreme Court to prohibit the assembly."

She added: "The first priority for NSW Police is always the safety of the wider community".

Refugee Action Coalition Sydney spokesman Ian Rintoul said it was a fundamental right to protest and health regulations should not be used to stifle that.

"Certainly we would contest (any legal challenge) because we put the form in, met with police, adhered to the requirements and had discussions about how the rally can be conducted in a safe way," Mr Rintoul said.

"There is a fundamental right to protest, a democratic right that needs to be defended and I don't think health regulations should be used to stifle that."

Mr Rintoul said he expected around 150 to 200 people to attend the rally, despite the 1200 who have already indicated they would attend.

The 2pm event, titled "Free the refugees: National day of action" is part of a wider day of protest being supported by "Pride in Protest", a Sydney-based collective of activists who say they campaign for refugee rights and indigenous justice.

Originally published as Court order to decide fate of weekend refugee rally