Protesters from a fathers' group were squirted with a hose and had rocks thrown at them as they demonstrated outside the home of an Auckland lawyer.
About 20 men and women were protesting with banners and megaphones outside the Pt Chevalier home of Ross France when a woman came from
behind a hedge and turned a hose on them.
Protest organiser Jim Bagnall said medium-sized scoria rocks were also hurled at the group but no one was hit.
"The rocks missed but they were aimed at our feet," he said. "She was screaming out at people to 'go home'. Well, we weren't going to go home for 15 minutes. We did tell her that."
Mr France refused to comment on the incident. When approached yesterday, his wife, Ina Kara-France, would also not comment.
Acting Sergeant Scott Leonard said police had investigated and a woman would appear in court on a charge of common assault.
He said the protest on Sunday had become heated but the alleged assault was "at the lower end of the scale".
Fathers' groups, including the Union of Fathers, have been staging noisy protests outside the homes of Family Court judges and lawyers, complaining they are treated unjustly.
It was the second time they had targeted Mr France's home in as many months.
In May, Principal Family Court Judge Peter Boshier said protesters were going beyond acceptable limits.
"It has all the hallmarks of personal vendetta by individuals who do not respect the legitimacy of the court," he said.
Mr Bagnall said the soaking would not deter the protesters.
"Some of the guys were saying this is the most fun they've had for ages."
