Climate protesters face arrest if they go ahead with plans to blockade the world's biggest coal port after the NSW Supreme Court backed police barring the action.
The court issued an order on Thursday deeming the planned protest at the Port of Newcastle from November 22 to 24 an unauthorised assembly after police moved to deny organisers a permit.
Hundreds of protesters were expected to take to the water in small craft for 30 hours, preventing access to the major coal export terminal.
More than 5000 people were expected to attend a simultaneous four-day "protestival" on land featuring live music, including a scheduled performance by former Midnight Oil frontman and federal environment minister Peter Garrett.
In his ruling, Justice Desmond Fagan said the impact of the blockade would be excessive, noting it went far beyond what those affected should be expected to tolerate in the name of legitimate protest.
The brunt would be felt by lawful commercial and recreational users of the port, he said.
"Whilst some inconvenience to non-participants must be accepted as an unavoidable concomitant of the rights of assembly and protest, the burden is usually slight and brief," he said.
The court also issued orders prohibiting the land-based protest, calling it "unheard of" for such an action to occupy public land for that length of time.
But police should not necessarily utilise their powers to break up the gathering if it occurred, Justice Fagan said.
"In the exercise of their judgment police may conclude that it is preferable to let the occupation of the park continue for the four days provided the assembly remains orderly," he said.
The court ruling does not prevent the protest from going ahead, but those involved lose protection from arrest and prosecution if they block traffic.
Organisers have vowed to move ahead with what they called "the people's blockade".
"We do have a right to assemble on public land and water, we will be exercising that right," Rising Tide spokesman Zack Schofield said.
"I can't comment on exactly what the police will be doing. I hope they'll do their job and facilitate peaceful protest."
Organisers would work with police to make the event as safe and accessible as possible, he added.
Justice Fagan had also raised concerns about the safety of the event and the ability of police to maintain order during a 30-hour protest on water.
He questioned whether it was wise to leave police without direct powers to break up the gathering if necessary, citing weather conditions and potential vessel accidents as "foreseeable risks".
Following the judgment, NSW Police repeated concerns about the safety of the protests.
"For their own safety and that of the other users of the port, we request that people who still attend this event refrain from entering the harbour ... with the intention to obstruct other users of the port, or engage in other forms of civil disobedience," a statement said.
NSW Council for Civil Liberties vice-president Lydia Shelly said police had created a perfect environment to enable the mass arrest of peaceful protesters by denying the application.
After initial pushback from police, organisers proposed a shorter 30-hour blockade rather than the original 50 hours, while also halving the time protesters would be camped in the area to four days.
Following a similar 30-hour blockade in 2023, more than 100 people were arrested after refusing to exit the water when the approved protest ended.
