TORONTO — Ontario is not a "dumping ground" for American sex offenders, Premier Dalton McGuinty said Tuesday as he urged Ottawa to fight a U.S. judge's decision to allow an American teacher who sexually abused a student to serve his probation time in Canada.

McGuinty urged the federal government to step in after a New York state court agreed to allow Malcolm Watson, convicted of sexually abusing a 15-year-old student, to return to St. Catharines, Ont., where he lives with his wife and three children.

"It's obviously not the precedent that we want to allow the Americans to establish, (and) it's not the kind of thing that we're prepared to accept," McGuinty said.

"We will certainly work with the federal government - and I hope we'll be of one mind in this regard - to ensure that we don't become some kind of dumping ground for convicted offenders (from) south of the border."

That was never the goal, said Erie County district attorney Frank Clark, who insisted that the plea agreement was designed to spare Watson's victim the grief of having to testify.

The sentence - Watson, 35, must spend three years on probation and stay out of the U.S., except for hearings and visits with his probation officer - was blown way out of proportion, said Clark. Nor was the court trying to supersede the jurisdiction of Canadian immigration authorities, he added.

"I feel like the King of England sending all my convicts to Australia, and we don't need another black eye like that," Clark said.

"I mean, that seems like such a horribly arrogant position for us to be taking. 'You're a crumb, so I'm going to banish you to Canada,' and that's not at all what happened."

The deal was put forward by Watson - a U.S. citizen who was aware he might not be allowed to cross back into the country where he's a landed immigrant - because he wanted out of the local limelight and a chance to patch things up with his family, said Clark.

The plan also appealed to the victim's parents, who did not want their daughter to take the stand, he added.

Watson is now back in Canada, said his lawyer, Oscar Smukler, who expressed surprise at the tumult the decision has triggered.

"He has lived in Canada with his wife for the last four years," Smukler said. "It's not like they're dumping him there. That's his home."

Smukler said he's reluctant to comment further on the case until Canadian immigration officials decide whether to step in.

Under the agreement accepted Monday by a Cheektowaga County court, Watson pleaded guilty to endangering the welfare of a child and sexual abuse in the third degree - charges that carry a maximum penalty of one year and 90 days jail, respectively.

He cannot have any contact with the victim and has been registered in the state of New York as a low-risk level 1 sex offender, which allows the public to access certain information about his offence and his residency.

The charges stem from an incident in April in which Watson, a popular English teacher at the elite Buffalo Seminary, was spotted in a car with a girl in a mall parking lot.

Clark said Watson and the girl appeared to have struck up a relationship that involved personal e-mails and spending time alone together, both on and off school property. School authorities deemed it inappropriate, but the relationship continued, he said.

Initial media reports from the U.S. that said Watson was convicted of having sex with the girl were incorrect, Clark added.

"He was never charged with intercourse. He never pleaded to intercourse. He never admitted to intercourse and she never claimed intercourse."

Throughout the relationship, Watson had been living with his family in the border city of Fort Erie, Ont., and commuting to his job in Buffalo. He had no prior criminal record and the court felt leniency seemed fair under the circumstances, Clark said.

American authorities can do little to monitor Watson in Canada, but his offence was a misdemeanour in the U.S. and carries few restrictions, Clark conceded.

"It is an honour system, but there are incentives on both sides for everybody to live up to what basically is an agreement that in many ways can't be enforced legally."

Conservative House Leader Bob Runciman called the decision "mind-boggling and horrific," and said Ontario's sex offender registry should include residents who are convicted of sex crimes outside the province.

"The Official Opposition is prepared to move on this quickly, and provide some level of protection from sex offenders who commit crimes outside our borders," Runciman said.

McGuinty said he would consider Runciman's idea, but expressed confidence Watson would be back before a U.S. court before Canada has to consider how to deal with him.

"I'm confident that if we work together with the federal government, we will ensure that these individuals are not admitted to the country in the first instance."