David Matas is highly critical of the decision of Federal Court Justice Michel Shore to send Lai Changxing back to China, calling it inconsistent, unpersuasive and wrongly decided.
The judgment ends an odyssey in Canada for Lai, who has been in and out of the custody of the Immigration and Refugee Board while he fought to remain in the country since he was arrested more than a decade ago.
"It is regrettable that his legal saga should end so poorly, with a judgment which gives undue deference to governmental authority," Matas said in a statement sent to The Canadian Press.
The court ruled Lai should be returned to China to face accusations he operated a multibillion-dollar smuggling operation.
The judge based his decision on "extraordinary assurances" from Chinese government officials that Lai would receive a legal defence and would not be tortured or executed.
Shore said it was assumed the promises of the Chinese government would be kept to save its "honour and face."
"A new, contractual government-to-government climate has been created by the assurances," Shore said in his 26-page ruling.
But Matas pulled apart the judgment in his five-page statement, saying Shore makes findings that are inconsistent with his ultimate conclusion to allow the deportation.
Shore recognized in his ruling that in the Chinese legal system a death sentence is not made public, that the Chinese government promised Canadian officials could attend open hearings — not closed hearings as might be the case for Lai, and that a lawyer retained by Lai in China would take instructions from the Communist Party, not Lai, Matas said.
But the judge was convinced by the existence of Chinese diplomatic assurances and their acceptance by the Canadian government, said Matas.
"The mere existence of assurances and their acceptance by the government were not proper grounds for a decision in this case adverse to Mr. Lai."
"The reasoning manifests exaggerated deference to both the Chinese and Canadian governments."
The judgment is final. The law does now allow an appeal from a stay decision.
Canada's border service agency would not say when Lai will actually be removed, but a spokeswoman said the policy is to enforce the order as soon as possible.
Lai, 53, escaped to Canada with his wife and three children in 1999. His application for refugee status was rejected in 2002.
Matas has steadfastly maintained Communist Party officials want to use Lai to set an example against corruption, and that he could be tortured or even be put to death if returned.
Alex Neve, secretary general of Amnesty International Canada, said his group has watched Lai's case since Lai arrived in Canada and has never thought it was safe to send him back.
Amnesty doesn't agree with the views coming from the Federal Court.
"China's record when it comes to torture and the death penalty is simply too entrenched. It's all about secrecy. It's pervasive."
China's former prime minister Zhu Rongji once said Lai should be executed three times over, and Matas told the Federal Court on Thursday that Lai had become the Communist Party's poster boy against corruption.
More reason, Neve said, that Lai shouldn't be returned to China.
"It's simply not credible in the context of on-going pervasive torture in the country. If China really meant it, when it comes to promise that it won't torture, then we would be seeing rapid progress in eradicating torture in the country."
Instead, Neve said, there has been a crackdown recently in China on human rights activists and people calling for democratic reform.
China has promised that Canadian officials will be able to monitor Lai while he's in jail, but Neve said they would have to be with the man 24 hours a day.