The information includes screenshots of an online chat between Vice Media reporter Ben Makuch and Farah Shirdon, a Canadian charged in absentia last September with leaving the country to join a banned terrorist group, threatening Canada and its allies, and related offences.
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Shirdon is suspected of involvement with the Islamic State group. Police said he travelled to Iraq or Syria join the group in March 2014.
Between June and October 2014 Makuch wrote three articles published by Vice Media about Shirdon's involvement with IS, based on communications with him.
Ontario Superior Court Justice Ian MacDonnell said in his ruling that the information is important evidence in a serious criminal case, in which there is a strong public interest.
The decision, however, raises concerns about compromising media independence and the impact on sources' willingness to share sensitive information with journalists.
"I'm very upset about (the decision)," Makuch told AFP.
"I think it's going to in a negative way affect the way journalists in Canada interact with sources and it could prevent sources from wanting to speak with journalists," he said.
Tom Henheffer, executive director of the Canadian Journalists For Free Expression advocacy group, echoed that view.
"Having journalists be an arm of law enforcement is an untenable position," he said.
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Henheffer suggested there may be a need for new legislation in Canada to shore up journalists' ability to protect their sources.
He noted, however, this raises counter-concerns, such as whether journalists deserve rights beyond those of average citizens, and whether the government should be left to decide who is a journalist and who is not, which would need to be defined in legislation.
In his decision, the judge noted that Shirdon was not a confidential source and that Vice had published most of the information sought by police, who simply needed proof Shirdon had been in the Middle East in order to prosecute him.
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