Given a choice between jail and exile to Canada, an American man chose Fort Erie, Ont. after being convicted for having sex with a 15-year-old girl.

Starting Monday, Malcolm Watson will stay out of the U.S. for three years as punishment for having a sexual relationship with the Buffalo, N.Y. student.

The sexual abuse sentence handed down by a New York State court only allows Watson to re-enter the U.S. to report to his probation officer.

Watson, 35, lives in Fort Erie with his Canadian wife and three children.

The former seminary teacher was arrested in April after a mall security guard noticed Watson and the girl sitting in a parked car for two hours.

District Attorney Frank Clark called the sentence "a little dicey."

Immigration lawyers in the U.S. are questioning whether the court has the authority to banish a citizen, The Associated Press reported.

Watson's defence lawyer Oscar Smukler was reportedly surprised by the unusual sentence. He is concerned that his client's new criminal record could prompt Canadian authorities to deny Watson entry.

"We did some research on the question of whether Canada might consider throwing (Watson) out, which would make him a man without a country," Smukler told AP.

Watson did have a choice of sentence. His alternative was to spend a year in jail.

With files from The Associated Press