Lawyers for an American anti-abortion activist will launch a High Court appeal against his deportation today, after his visa was cancelled by the Federal Government.

Troy Newman spent last night detained at Melbourne Airport, after arriving on a flight from Los Angeles without a visa.

Lawyers representing him have launched an appeal against his deportation, with the matter to be heard by the High Court in Melbourne.

Mr Newman co-authored a book that questioned why doctors who abort babies are not executed, but claims he has done nothing wrong.

His wife Melissa Newman told 7:30 the Australian Government should let him go.

"I don't know what they're afraid of. I don't know what they think he's going to do here," she said.

She has also defended moves by the couple to continue their journey to Australia, after being told at Denver Airport he did not have a valid visa to make the journey.

"We just went to another airline and booked our tickets to LAX [Los Angeles International Airport]. When we got to LAX we had our boarding pass, already, because they issued it in Wichita from LAX to Melbourne," Ms Newman said.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 5 minutes 36 seconds 5 m Troy Newman - the American anti-abortion campaigner facing deportation from Australia

"They let us on the plane without any trouble at all."

Coalition MP George Christensen, a pro-life supporter, said while he did not condone Mr Newman's comments, he should be afforded due process.

"If you're coming to Australia to talk about your belief and the right to life, I don't think anyone would want to stop you, and certainly I couldn't see [Immigration Minister] Peter Dutton stopping anyone from coming to expressing that view," he said.

"But if your view is that people should be executed, then regardless of who you are and what other views you have, I think you're going to get pulled up, and rightly so."

Mr Christensen said supporters of Mr Newman had questioned the reasons behind his visa being cancelled.

"The question is out there as to whether or not these views are reflective of his writings and what he said in the past, and I suppose that will come out in the High Court," he said.

"I know that this gentlemen says that he has not advocated for that, and certainly people in the right-to-life movement say this fellow hasn't advocated for that either.

"So everyone has their day in court."

Labor MP welcomes visa cancellation

Labor MP Terri Butler has welcomed moves by the Federal Government to cancel Mr Newman's visa.

"We are talking here about someone who has written a book saying that doctors should be executed for doing something that's been legal in the US since the 70s," she said.

"If this was someone who'd called for the execution of journalists for reporting, for example, I suspect that the minister would have made the same decision."

Mr Newman is the head of anti-abortion organisation Operation Rescue and was due to speak at events run by the group Right to Life Australia.

He is also the co-author of the book Their Blood Cries Out, which was published in 2000.

In the book, he questions why doctors who perform abortions are not executed and asks why women or men who request the procedure are not charged with murder.