A court in China has ordered a retrial for a Canadian man who was sentenced last month after being found guilty on drug-smuggling charge — potentially adding more pressure to the fraught Canada-China relationship.

The Higher People's Court of Liaoning Province heard an appeal Saturday from Robert Lloyd Schellenberg, who was given a 15-year prison sentence last month for his involvement in international drug-trafficking activities.

At the appeal hearing, prosecutors argued Schellenberg was likely to be part of an international drug smuggling operation.

In its decision, the appeals court ruled the "light punishment" of the 15-year sentence was "obviously inappropriate" and sent the case back to the Dalian Intermediate People's Court for retrial. That court, in the eastern port city of Dalian, began its hearing on the case back in March 2016.

In the decision, the court noted that Canadian diplomats were in court for the appeal.

It's not clear yet who is representing Schellenberg or when the retrial may take place.

A spokesperson for Global Affairs Canada said the government is continuing to offer consular services.

"Global Affairs Canada has been following this case for several years and has been providing consular assistance to the Canadian citizen since they were first detained in Liaoning, China. We will continue to provide consular services to them and their family," said Richard Walker in an email to CBC News.

"Due to the provisions under the Privacy Act, no further information can be disclosed."

Heightened tension between Canada, China

Schellenberg has been detained in Liaoning province since 2014, predating the detention of two Canadians — former diplomat Michael Kovrig and businessman Michael Spavor ​— who were picked up by Chinese authorities over so-called national security concerns shortly after Canada arrested a Chinese tech executive at the request of the United States.

Huawei chief financial officer Meng Wanzhou was arrested in Vancouver on Dec. 1. She has since been released on bail and remains under surveillance as she prepares to fight extradition to the U.S., which accuses her of fraud and lying to banks about business activities in Iran.

Chinese officials haven't called the arrests of Kovrig and Spavor acts of retaliation but they have pointedly compared the cases, insisting the men were detained in accordance with Chinese laws while maintaining that Meng's arrest was illegal.

A Chinese Foreign Ministry spokesperson said Canadians Michael Kovrig, right, and Michael Spavor were arrested for allegedly undermining Chinese 'national security,' while Huawei executive Meng Wanzhou was arrested 'illegally' in Canada for the U.S. (The Associated Press/International Crisis Group/The Canadian Press)

While Schellenberg's trial and sentencing received little media attention, Chinese officials invited several foreign news organizations to cover his appeal hearing on Saturday along with state-run media.

Lynette Ong, an associate professor in the University of Toronto's department of political science and Asian Institute, said that means the government likely wants the world to watch.

"They are airing it in public as a showcase of their power and potential to put pressure on Canada," she said.

"I think the authorities have the potential to intervene and the capacity, but it is still possible that he can get a fair trial… I think Chinese authorities are trying to show the world that, 'Look, see, this is potentially another Canadian in our hands that we can apply pressure on you.' But it could mean nothing more than that."

'Not a good time' for a retrial

China treats drugs offences seriously and is known to use severe punishment.

In 2009 China executed a Briton caught smuggling heroin, prompting an outcry back in the United Kingdom. Gordon Brown, the British prime minister at the time, condemned the killing of Akmal Shaikh, while the man's friends and supporters claimed he was mentally unstable and was unwittingly lured into the crime.​

As tension in the Canada-China relationship continues to simmer, Gordon Houlden, director of the the University of Alberta's China Institute, said things could be harder for Schellenberg and his legal team.

"I can't see inside the judge's head or what his instructions from the party might be, but this is just not a good time. We're not going to get the benefit of doubt and the penalties may be more severe," he said.

"Their system works very much more differently than ours. There is potential for party intervention in sensitive cases, in a way that's simply not possible in Canada."

On Friday, Global Affairs Canada said Sarah McIver, a teacher from Alberta who was detained in China after the arrests of Kovrig and Spavor, has returned to Canada after being released from custody.

She was detained due to a work-permit issue.