John Wrenshall, seen in an undated handout photo, was convicted in 1997 of sexual assault involving members of a Calgary boys' choir.

A former Calgary man arrested in connection with a child sex business in Thailand has been convicted twice in Canada on sex-related charges involving young boys.

Thailand resident John Wrenshall, 62, was arrested at Heathrow Airport on Monday morning by London police and U.S. immigration agents.

The charges stem from Wrenshall's alleged involvement with U.S. citizens who travelled to Thailand to sexually abuse children and produce "visual depictions" of the abuse, the Justice Department said.

According to the unsealed indictment and court documents, Wrenshall, 62, had frequent access to Thai boys, some as young as six years old, at his home in Thailand.

Wrenshall lived and worked in Calgary 12 years ago. He was convicted in 1997 of sexual assault involving members of a Calgary boys' choir.

According to Calgary Herald articles from that time, Wrenshall lured boys over three decades, telling them he was working on a study on pre-teen boys' sexuality. He was sentenced to a year in jail and two years probation.

The former Calgary scout leader was convicted of a similar offence in 1970 and given a suspended sentence with two years' probation, according to the Herald.

Wrenshall's family members in Canada say they are devastated by the news, adding they have been estranged for years.

David Butt, a spokesman with the Kids' Internet Safety Alliance, said despite Wrenshall's arrest, there are shortcomings in Canadian law.

"We've seen the United States involved, the U.K. involved and obviously Thai authorities involved," he said. "But where are the Canadians in all of this? We don't have on the ground ability to investigate our nationals when they go abroad to commit these kinds of serious offences."

But police in Canada are trumpeting their investigation.

"It basically just shows what international and national co-operation can do. The reality is, the reason Mr. Wrenshall is in custody today is because of great co-operation between national and international agencies regarding this matter," said Sgt. Phil Crouch of RCMP.

Conviction could bring 15 years in prison per charge

Earlier this week, Wrenshall was charged by the U.S. government with one count of conspiracy to engage in sex tourism, two counts of aiding and abetting sex tourism, one count of conspiring to produce child pornography, seven counts of producing child pornography and seven counts of distributing child pornography, the Justice Department said in a release.

The indictment alleges that as early as May 2000, Wrenshall helped arrange trips to his home in Thailand during which U.S. citizens and others paid him money to engage in sexual acts with the boys, sometimes for weeks at a time. Wrenshall's alleged customers were allowed to videotape and photograph their abuse.

He was being detained pending extradition from Britain to face the charges in the U.S.

If convicted, Wrenshall faces up to 15 years in prison for each count of sex tourism, a minimum of 10 years and a maximum of 20 years in prison for each count of producing child pornography, and as many as 15 years in prison for distributing child pornography, the Justice Department said. He also faces a fine of up to $250,000 US per count, it said.