A spokeswoman for Immigration Minister Peter Dutton said: "I can confirm that Mr Newman-Mariotti has departed Australia."

On Friday, The High Court threw out an emergency bid by Mr Newman to restrain authorities from removing him from Australia.

Tom Howe, QC, who appeared for Immigration Minister Peter Dutton, said the minister wanted to remove Mr Newman, who was being held at Melbourne's Maribyrnong detention centre, "at the earliest opportunity".

Following the ruling, Mr Dutton issued a statement announcing he had instructed his department to "expedite" Mr Newman's removal.

Mr Newman, who was due to begin a national speaking tour for Right to Life Australia in Melbourne on Friday night, had his visa revoked by the Immigration Department as he was on his way to Australia.

The department believed Mr Newman's presence would be "a threat to good order", and his views on abortion could lead to protests that would compromise the safety and wellbeing of women seeking legal medical procedures and of the medical staff performing those procedures.

Australian Border Force officers detained Mr Newman on his arrival in Melbourne and he spent Thursday night  at the Maribyrnong detention centre.

Mr Howe told the High Court this was "the natural consequence of his decision to come to Australia in circumstances where he was informed he wasn't entitled to".

Justice Geoffrey Nettle said while there was an implied right in the Constitution to freedom of political communication, that right was given to Australian citizens.

"Like everyone else in this country he is bound by lawful authority and must obey ... he does not come to this court with clean hands."

Justice Nettle said it had not been proven that Mr Newman had advocated the death penalty for doctors who perform abortion, as had been alleged, and there was no evidence that the anti-abortion protests he had been involved with in the United States had been violent.

The department cancelled Mr Newman's visa and sent him an email to alert him to the fact. When the email bounced back, a copy of the email was posted to him.

But by this time, Mr Newman was in a plane on the way to Australia.

However, Justice Nettle said Mr Newman had been made aware by airline staff that his visa had been revoked and he could have stayed in America and engaged a legal team to fight the matter there, rather than board another plane.

Mr Newman's wife Melissa was in court to hear the verdict with supporters, but would not talk to reporters afterwards.

Lawyers for Mr Dutton and Mr Newman agreed to reappear in court on October 30, when the question of whether the department was legally entitled to cancel Mr Newman's visa will be decided.

In his statement following the High Court ruling, Mr Dutton said Mr Newman had been treated in the same manner "as any other illegal arrival".

"Any person who enters Australia without a valid visa and does not have a lawful basis to remain in Australia is expected to depart," Mr Dutton said.

"His detention and removal is entirely related to his decision to openly flout Australian law and travel to Australia without a valid visa."

Mr Dutton said he had instructed his department to investigate how Mr Newman was able to board his United Airlines flight for Australia despite alerts being issued in the Movement Alert List system.

"Any airline involved faces a fine for carriage of a person who does not hold a valid visa," he said.

The court ruling scuppers Mr Newman's national speaking tour, which was to visit Melbourne, Hobart, Sydney, Brisbane and Cairns.

Right to Life chief executive Katrina Hellar claimed Mr Newman "was not being deported" and she believed he and his wife would leave Australia voluntarily.

"He is sick of it. He is fed up with Australia. He can't understand it," Dr Hellar said.

"Because in America they have freedom of speech. We have freedom of speech, we have freedom of political communication."

She said Mr Newman had been stripped of his mobile phone at Melbourne's Maribyrnong detention centre and "I think he'd be upset about that. He's probably missing his phone."

Labor MP Terri Butler said the department was right to cancel Mr Newman's visa and she welcomed the court's decision.

"He came to Australia knowing that he didn't have a visa ... directly flouting our immigration laws," she said.

"To think that he is above the law in that way I think really gives us an insight into the sort of person that we're dealing with."

Ms Butler said Australia was a democracy that allowed "frank discussion" on polarising issues including abortion.

"But we don't welcome extremists into our country," she said.