Ottawa lawyer Gordon Cameron — the amicus curiae, or friend of the high court — says in a written submission it is "not an appropriate case" for the justices to examine.
The federal government has urged the Supreme Court to hear the case, saying the Canadian Security Intelligence Service has been left "in the dark" about when a judge's approval is needed to monitor suspected Canadian extremists abroad.
Federal lawyers say lower courts made "significant errors" in dealing with the sensitive matter.
In a key 2013 ruling, Federal Court Justice Richard Mosley criticized CSIS over a request for warrants to track two Canadians with technical help from the Communications Security Establishment, Canada's electronic spy agency.
Mosley said CSIS breached its duty of candour by failing to disclose that CSE's foreign counterparts in the Five Eyes intelligence network — the United States, Britain, Australia and New Zealand — could be called upon to help.
He also warned that CSIS and CSE were incurring the risk that Canadian targets "may be detained or otherwise harmed" as a result of the use of the intercepted communications by foreign agencies.
The Federal Court of Appeal upheld Mosley's judgment in a ruling made public last month.
In its request to the Supreme Court for a hearing, federal lawyers argue that Canada "must pay close attention to the threatening activities of its own citizens, wherever they may be."
"Certainty as to how it can engage in that monitoring according to law is a matter of public importance."
The Court of Appeal declared that a warrant is required when CSIS — either directly or through the auspices of a foreign spy service — uses "intrusive" methods such as interception of telecommunications. It said such warrants could be issued when the interception "is lawful where it occurs."
Federal lawyers, however, said they had many questions about what the appeal court meant.
The role of Cameron, as the amicus, is to assist the Supreme Court by probing the Crown's evidence and arguments — with no obligation to agree or disagree, said University of Ottawa historian and intelligence expert Wesley Wark.
In his submission to the high court, Cameron notes the government recently introduced legislation that would explicitly allow CSIS to seek a warrant to investigate a security threat beyond Canada's borders — legislation that could make the central issue moot.
If the high court decides to hear the case against his advice, it should wait "a reasonable period" to gauge the legislation's effect, Cameron says.
On the issue of candour, the government says there must be clear guidance on the degree of transparency required.
Cameron argues the appeal court was correct on that point and "therefore there is no reason to grant leave to appeal on this issue."
Wark agrees with Cameron that CSIS breached its duty to be more forthcoming. But he disagrees that the bill before Parliament makes the idea of a Supreme Court hearing redundant. The section of the bill dealing with warrant powers makes no mention of whether such warrants could be used to obtain the help of foreign powers — either directly or through CSE, he said.
It is precisely these issues the government is asking the Supreme Court to clarify, Wark added.
It could be weeks before the Supreme Court decides whether to hear the case.
The government says the issues could generally be argued in open court, though some proceedings might go behind closed doors due to national security concerns.
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