Outside the court, Stop the War Coalition spokesman Alex Bainbridge said police had ambushed the protesters with news they would erect the King Street barrier. "We were always under the understanding that these areas were open to the public,'' he said.

Mr Bainbridge said the coalition would meet tonight to consider its options, and that it might still go ahead with plans that would put protesters at odds with police. "The court has made very clear that we have got a right to protest,'' he said. "The court order today prohibits nothing, our rally and demonstration will be going ahead.

"As we have always said we intend for this to be a peaceful protest. "We have never ruled out non-violent civil disobedience.''

During his judgment, Justice Michael Adams agreed freedom of speech was paramount in a democratic society. He said ending the rally at that police barrier would make it a target. "In my view, the attitude of the Commissioner to this application is a reasonable one and accordingly I grant the orders sought,'' he said. He agreed with police that ending the rally at King Street would cause problems because of the narrowness of the area, and the lack of exit points.

The protesters had floated an alternative "sit-down protest'' in front of the police line at George and King streets, after which the crowd would disperse. But the barrister for the police, Michael Spartalis, told the court that the Commissioner would also oppose this plan.

Mr Spartalis said the Commissioner had indicated he would approve an alternative route, from Town Hall down Park Street to Hyde Park. Earlier the court heard a police riot squad chief say Sydney should brace itself for an unprecedented level of violence during the march. The "grave concerns'' of police were aired as they faced off with the Stop Bush Coalition in the court over its planned marching route.

Justice Adams strongly supported the protesters' rights to demonstrate on what were clearly topical and important issues. "There is presently being held in Sydney an international conference which involves a number of visiting dignitaries,'' he told the court.

"Amongst these visiting dignitaries is the President of the United States. "Mr Bush excites perhaps indifference in some, support in others and anger in others. "All these are feelings which no doubt have a legitimate foundation depending on the experience, character and cast of mind of the person who has them.''

The wars in Iraq and Afghanistan and climate change were among the reasons behind such "strong feelings'', which found their expression in public assembly and lawful protest, he said. "All these are perfectly reasonable; they are normal, acceptable modes of behaviour in a democracy.''

However, Justice Adams said it would be foolish to assume everyone present at the protest would be peacefully minded. "I don't have any doubt that the overwhelming majority of those attending the demonstration wish to exercise their democratic right of lawful assembly and freedom of expression ... and who would abhor violence,'' Justice Adams said. "But I think it's Pollyanna-ish to think that everyone there will share that view.''

In the court action, police opposed the coalition's original protest route from Town Hall, along George Street, through Martin Place and on to Hyde Park. However, with the barrier to be erected at George and King streets, the court heard that this route would, in any case, be blocked to the marchers.

Police said if their expectations of 20,000 marchers were met, any push against the barrier could result in "crowd crush'' and "horrendous consequences''. "Police lines will come under attack and a full-scale riot is probable [if the route was approved," Chief Superintendent Steven Cullen told the court. Chief Superintendent Cullen told the court he held "grave concerns'' for public safety during the protests.

Acting for the protesters, barrister Michael Bozic rejected the police's preferred Park Street route, saying the march aimed to highlight, among other things, the police response to APEC. - with AAP