TORONTO -- The federal government has the 鈥渦nequivocal鈥 authority to intervene in the extradition case of a Chinese executive, even if it doesn鈥檛 want to exercise it, says a prominent defence lawyer.

Brian Greenspan told CTV鈥檚 Power Play Tuesday that under the Extradition Act, the justice minister can withdraw the authority to proceed with the extradition of Huawei executive Meng Wanzhou, who was arrested by Canadian authorities in Vancouver in December 2018 after the United States requested her extradition.

While her arrest sparked outrage in China and a rapid cooling of relations between Canada and China,

the Canadian government has repeatedly insisted that the court process be allowed to unfold without political interference.

It has stuck to that message, despite China鈥檚 detention of Canadians Michael Spavor and Michael Kovrig since shortly after Meng鈥檚 arrest.

But Greenspan said the judicial process includes what he called a 鈥渟afety valve,鈥 which allows the minister to determine if an extradition should proceed.

"The process itself is initiated by the minister of justice, initiated with an authority to proceed, and during that first phase of extradition, which is the judicial process, there's express language which permits the withdrawal of that authority to proceed at any time," Greenspan said.

Earlier on Tuesday, Greenspan told CTV News Channel that an overhaul of the Extradition Act in 1999 gives the justice minister 鈥渦nfettered discretion to withdraw an extradition at any time during the judicial phase of extradition,鈥 which offers the federal government a 鈥渧ery clear option.鈥

鈥淚 don鈥檛 express, nor would I express an opinion as to whether they ought to exercise it or whether they should withdraw, that鈥檚 a question that鈥檚 political in nature,鈥 Greenspan said. 鈥淭he best interests of Canada have to be considered. That鈥檚 a question for the government. But whether they can in fact, intervene at this stage, in my view is very clear: they can.鈥

But Treasury Board president Jean-Yves Duclos emphasized the importance of judicial independence when he was asked about this option to withdraw the extradition during his Tuesday press conference.

"In Canada, we have not only a tradition but a responsibility to work in a manner that is supportive of the integrity and the independence of our justice system," Duclos said.

"This is very important for the way in which our institutions work in Canada, we have a separation between the executive, and the legislative, as well as the judicial systems, and that's exactly what it should be."

But as Meng鈥檚 case inches through hearings at the B.C. Supreme Court, and she remains out on bail in Vancouver, Spavor, a businessman, and Kovrig, a former diplomat, have languished in Chinese custody for more than 560 days.

The Canadian government has repeatedly described their detention as retaliation for Meng鈥檚 arrest and an attempt to exert pressure on Canada, but China denies that. The Chinese government charged Spavor and Kovrig with espionage Friday.

Prime Minister Justin Trudeau condemned the charges, saying Canada was 鈥渦sing a wide range of public and private measures鈥 to secure the release of the men. But he is facing growing criticism from opposition parties who say Ottawa must do more.

Duclos said the government is 鈥渧ery preoccupied and saddened and angered鈥 by their detention, which he called 鈥渢otally unacceptable.鈥

鈥淭here are all sorts of things we don鈥檛 understand, including the fact they don鈥檛 have access to consular services, which is an obligation under international treaties. We are making that well understood and well felt by the Chinese government.鈥

But he said the independence of the Canadian justice system is important to its citizens and the country鈥檚 international reputation.

鈥淲e believe our anger and frustration are also shared by many partners outside of Canada and some of them have voiced their level of anger and frustration. I think this is something essential.鈥

U.S. authorities have charged Meng, the daughter of the founder of Huawei and the giant telecom鈥檚 chief financial officer, with fraud alleging she circumvented American sanctions on Iran.

The diplomatic war of words seems to be escalating.

U.S. Secretary of State Mike Pompeo said in a statement Monday that the Chinese prosecution of the two Canadians is 鈥減olitically motivated and completely groundless.鈥 He said the 鈥渦njustified detentions鈥 are aimed at coercing Canada. He called for the immediate release of the two men.

A Chinese Foreign Affairs spokesperson said Tuesday that talk of 鈥減olitical motives, improper detention and arbitrary arrests鈥 applies to Canada and the U.S., not China.

The U.S. has 鈥渁bused its national power鈥 and the 鈥渃ase of Meng Wanzhou was completely a serious political incident,鈥 said Zhao Lijian at a press conference in Beijing.

鈥淚f the arbitrary arrest of Meng Wanzhou by the U.S. and Canada is the so-called 鈥榡udicial independence,鈥 why do they use various pretexts to interfere in the independent handling of cases by the Chinese judicial department? Such unfounded countercharges based on double standards refresh our understanding of the lower limit of the U.S. and Canadian politicians.鈥