I found an interesting document (thesis) written by Yan Campagnolo titled 'Reconciling Cabinet Secrecy With The Rule Of Law' in 2018. There is a section buried deep in the thesis titled "Section 39 is Procedurally Unfair'. In this section he discusses that litigants faced with the invocation of Section 39 wrongly argued against not being able to see the government evidence, but should have instead argued that the decision-maker (the one who decides that Section 39 should be invoked) is not independent and impartial and instead acts as judge and jury against the plaintiffs motion, without any chance for the actual sitting judge to see the evidence. The paragraph I'm referring to follows:
While the litigants were on to something, the thrust of their argument was misplaced.
What makes the decision-making process set out under section 39 procedurally unfair is not
the fact that it may lead to the exclusion of relevant evidence for public policy reasons; rather,
it is the fact that the decision to exclude the evidence is made by someone who is seemingly
biased, namely, “a minister of the Crown or the Clerk of the Privy Council.” Subsection 39(1)
gives members of the executive branch a very broad discretion to decide whether relevant
evidence should be withheld in proceedings where the Government is a party, in breach of
the natural justice principle nemo judex in sua causa (no one may be judge in his own cause).
This attribute differentiates section 39 from the other existing privileges and immunities.
The Minister or the Clerk is not just “objecting” to the production of information, he or she is
finally and conclusively “deciding” the matter. No other privilege or immunity enables a
litigating party to decide what evidence should be excluded from the proceedings. This is
normally a matter for the judge to decide. Hence, the problem is not so much that section 39
prevents a party from adequately stating his or her case, the problem is that the individual
who has the power to exclude the evidence is not “without bias.”
The link to the thesis (302 pages long) is
https://tspace.library.utoronto.ca/bitstream/1807/89682/3/Campagnolo_Yan_201806_SJD_thesis.pdf
I hope that Wolverine .303 has the opportunity to read this.