AMERICAN peace activist Scott Parkin arrived back in the US today after spending five days in a Melbourne jail as a "national security risk".

The 36-year-old Texan history teacher was also given a bill for almost $11,700 after his brush with Australian authorities. Mr Parkin said he was made to feel like a terrorist and a criminal and remained baffled as to why six police officers "snatched him off the street" as he left a Melbourne cafe last Saturday.

He said he was interrogated and spent the next five days in solitary confinement.

He was escorted by two Victorian correctional officers on a Qantas passenger plane which left Melbourne yesterday, arriving in Los Angeles this morning.

"I'm just completely baffled by all of this," said Mr Parkin, surrounded by Australian TV cameras and media, soon after his arrival at Los Angeles international airport.

Mr Parkin was in Australia as part of a six-month holiday to Australia, New Zealand and Asia. He arrived on June 1.

An activist for 15 years, he said he gave talks while in Australia about the war in Iraq and helped organise one protest against US energy company Halliburton.

"In the talks I gave I wasn't even openly critical of Australia," Mr Parkin said.

"I was being openly critical of the US occupation (of Iraq) and I was being openly critical of Halliburton."

Mr Parkin said authorities never made it clear why he had been arrested.

"They were very vague," he said. "They said I violated sections of the migration Act and they said I was a direct or indirect risk to their national security."

Mr Parkin said he was housed alone in a jail cell that contained two concrete slabs to sleep on, a TV set and a sink.

"They gave me three couch cushions and three really crummy blankets and fed me three times a day," he said.

Mr Parkin was also handed a bill for almost $11,700. It included $4235.03 for his airfare back to LA and $6675.39 for the return airfares of his two corrective services escorts as well as their accommodation in Los Angeles.

"They're staying in Anaheim on Disneyland Drive I heard," Mr Parkin quipped.

The five-day stay at the Melbourne Assessment Prison will cost him another $777.

"They said if I ever decided to return to Australia I'd have to pay them back," Mr Parkin said.

The activist was also banned from entering Australia for three years. He plans to fight his removal from Australia and is desperate to find out why authorities were concerned about him.

"I'd love to know the assessment in which the Australian Security Intelligence Organisation (ASIO) made of me to lock me up for five days in solitary confinement and then remove me from the country essentially forcibly," Mr Parkin said.

Mr Parkin warned the incident raised great concerns about freedom of speech in Australia and the US.

"I think we are seeing a crisis in freedom of speech and freedom of expression in Australia, the United States and lots of places and people need to be aware," he said.

Most American tourists leave Australia with an Akubra, a didgeridoo, a cheesy t-shirt or a coffee mug.

Scott Parkin, a history teacher from Houston, Texas, and a self-described peace activist, left with an outstanding bill for $A11,688.34.

The hefty bill wasn't racked up from fancy hotels or day trips scuba diving on the Great Barrier Reef.

The bill was from the Australian government.

More specifically, the Department of Immigration and Multicultural and Indigenous Affairs.

Four nights in an Australian jail, with three meals a day, apparently is as expensive as a three or four star Melbourne hotel.

Parkin, who was deported from Australia on Thursday for being a security risk, showed off the bill to journalists when he arrived at Los Angeles international airport, accompanied by two Australian escorts.

The headline on the bill, stamped with the Australian coat of arms, reads: Notice in respect of the detention/removal costs.

The Australian government has charged Parkin $A777.92 for four days in the not-so-luxurious Melbourne Assessment Prison.

That's $A194.48 per day.

A quick check of the going rates at Melbourne's better hotels shows that a prison cell is more expensive than, say, the $A175.00 a night charged for some rooms by the Eden on the Park hotel, overlooking Albert Park.

Guests at the Eden on the Park receive a complimentary kimono, can swim in an indoor pool or work out in the rooftop gym.

Parkin's facilities were a little different over at the Melbourne Assessment Prison.

This is how he described his cell.

"It was a room with two concrete slabs, a television, toilet and a sink," said 36-year-old Parkin, who was alone in his cell.

"They gave me three couch cushions and three really crummy blankets and fed me three times a day."

Parkin also was hit with the cost of his one-way Qantas airfare from Melbourne to LA.

That came to $A4,235.03.

The bill also demands Parkin pay $A6,675.39 for the return airfares of the two corrective services officers who accompanied him and handed him over to American authorities in Los Angeles.

But that's not all.

The $A6,675.39 includes hotel accommodation in Los Angeles for the two officers.

The officers will have plenty to do during their stay in sunny, southern California at Parkin's expense. Maybe even a visit to the world's most famous theme park.

"They're staying in Anaheim on Disneyland Drive I heard," Parkin said.

The bill also tells Parkin to "please forward the above amount as soon as possible" to the Australian embassy in Washington DC.

If not, the letter warns the government can take him to court to recover the money.

Parkin, who is stunned that Australian authorities would deem him a security risk and throw him out of the country and then ask him to pay for it, says he will fight it in court.

Besides, he was not totally happy with the service he received on the flight back to LA.

While his air ticket cost top dollar, his two escorts refused to let him enjoy Qantas' well stocked inflight bar during the 14-hour flight.

"They wouldn't even let me buy a beer," Parkin said.