The group of about 300 men in masks and paramilitary uniforms is accused of making threatening phone calls, giving out accusatory pamphlets and broadcasting allegations against women by megaphone.
But the militants' leader, John Abbott, said the Blackshirts were simply exercising their right to protest.
"We're not here to win a popularity contest, we're here to encourage and protect and defend marriage, the family and the children."
Warning
The group was set up to contest the decisions of the Family Court, which settles custody and divorce cases.
The office of Victoria's Attorney General Rob Hulls said on Thursday it had written to Mr Abbott warning that members of his group could face criminal prosecution if they were found to be harassing women.
But Mr Abbott in turn threatened to sue Mr Hulls and said he would continue his campaign.
"I will continue until the very issue, the very essence of marriage is re-established," he told Melbourne radio station 3AW.
Neighbourhood watch
He acknowledged that his group staged demonstrations under police supervision in order to educate neighbourhoods of "unsavoury actions" such as extramarital affairs and child abuse.
But Victorian Premier Steve Bracks suggested that the Blackshirts should be seeking counselling over the breakdown of their marriages rather than pursuing their current activities.
"Desist from what you're doing because it's causing undue harm to people who want to go about their business," Mr Bracks said on ABC radio.