Campbell J. found that the parol evidence rule prevented the Minister from bringing extrinsic evidence that would have shown that the taxpayer was disingenuous in the way it characterized one of its business contracts for tax purposes. As per Shell Caada Ltd. v. The Queen, [1999] 3 S.C.R. 622, 99 DTC 5669, while "courts must be sensitive to the economic realities" of a transaction, these "realities" cannot trump a bona fide legal relationship created through an unambiguous contract.
Moreover, in the same case the taxpayer had previously been barred from bringing extrinsic evidence concerning the same agreement - to allow the Minister to bring extrinsic evidence would be unfair.