The New South Wales assistant police commissioner has issued a letter to the organisers of this evening's pro-Wikileaks rally in Sydney, directly opposing the march.
The protesters had intended to meet at Sydney's Town Hall before marching on to the US Consulate building at Martin Place, less than a kilometre away.
The protest is in aid of free speech after several high profile organisations withdrew their support from Wikileaks and to shine light on Julian Assange's recent arrest in London.
The letter (PDF) — sent directly to Pirate Party member Rodney Serkowski from M.J. Murdoch, assistant commissioner and commander of Central Metropolitan Region — said that under Section 23 of the Summary Offences Act, the rally must be authorised by a court to be protected against various offences.
The assistant commissioner added that without a court notice authorising the rally, protesters and organisers would not have the support of the NSW Police Service.
"Under Section 26 of the Summary Offences Act, I am advising you that I oppose the holding of your public assembly," the assistant commissioner said in his correspondence.
"Please note that without an authorised public assembly you do not have protection for obstruction type offences," Murdoch added.
Serkowski told ZDNet Australia of his anger and disappointment over the letter, saying that opposing the rally violates citizen's rights to free assembly.
"This isn't your regular bunch of rag-tag protesters, these are mainstream people that are really upset about what is happening to [Julian] Assange and of course what's happening to Wikileaks in general," Serkowski said.
Serkowski said that despite the notice, the rally would go ahead at the Sydney Town Hall this evening.
"The march will still be going ahead and as far as I'm aware, all the speakers will still be coming along," he added.
However, Serkowski added that the protest may not march to the US Consulate as originally planned.
"We were looking to negotiate alternate routes so as to minimise the impact on traffic. We don't want to bring the city to a halt, but unfortunately they didn't want to agree to anything ... I've never had to deal with them being so against [an event]," he said.
Serkowski claimed that the NSW Police cited Oprah Winfrey's Sydney visit as one of the reasons it could not lend its support to the rally.
"They've shut down half the city for a talk show host, surely when a few people want to exercise their democratic right and walk down the road for 30 minutes to protest one of the great injustices of our time [they are opposed]," said Serkowski.
"It's shameful," he added.
The NSW Police said in a statement that the reason the assistant commissioner opposed the march in his correspondence was due to the organisers of the event failing to submit complete paperwork in a timely manner.
"The group gave one day's notice before the march saying that they intended to march on George Street to Martin Place in peak hour, but this was not acceptable to the police," the service said in a statement.
The police offered alternatives including holding a static protest, marching an alternate route or holding the march at another time.
"A similar protest last Friday was assisted by police despite the application not complying with regulations then. Police explained the requirements then and [the organisers] were well [aware] of the requirements," the police added.
The Australian Pirate Party told its followers via social messaging service Twitter that it is still working with the NSW Police to ensure public safety, despite the commissioner's opposition of the rally.
This latest rally marks the second protest in Sydney against Julian Assange's imprisonment, with the first attracting over 1000 attendees. Other rallies have been held in the other state capitals, with more to follow.