Kovrig is an analyst on northeast Asia for the International Crisis Group think tank who took a leave of absence from the Canadian government.
China seized a pair of Canadians, Michael Kovrig and Michael Spavor, on December 10 in the aftermath of Canada's arrest of a Huawei Technologies Co. executive, Meng Wanzhou.
The two Canadians were held last month after the arrest of Meng Wanzhou, the chief financial officer of Huawei Technologies, in Vancouver on Dec 1, at the request of the United States which has accused her of violating Iranian sanctions. She is out on bail. He encouraged China to do the same.
According to Reuters, Trudeau told the reporters in the western Canadian city of Regina in Saskatchewan, "It is unfortunate that China has arbitrarily and unfairly detained two Canadian citizens".
"This is something that we are engaged right now both with Chinese officials and with our partners around the world where there is a concern for the need for all countries to do like Canada and to respect the rule of law and the independence of our judicial processes". "We have a justice system that is not subject to political interference".
It was the first public comment on Kovrig's status.
Trudeau called U.S. President Donald Trump about it and the White House called the arrests of the Canadians "unlawful".
According to the Vienna Convention, persons carrying a diplomatic passport enjoy immunity when they are overseas.
Officials previously said he wasn't protected by diplomatic immunity.