[89] At paragraph 104, McLachlin J. set out the duty of ordinary prudence:
The matter comes down to this. The duty on the Crown as fiduciary was “that of a man of ordinary prudence in managing his own affairs”: Fales v. Canada Permanent Trust Co., [1976 CanLII 14 (SCC),] [1977] 2 S.C.R. 302, at p. 315. A reasonable person does not inadvertently give away a potentially valuable asset which has already demonstrated earning potential. Nor does a reasonable person give away for no consideration what it will cost him nothing to keep and which may one day possess value, however remote the possibility. The Crown managing its own affairs reserved out its minerals. It should have done the same for the Band.
[90] At paragraph 22 of Blueberry River, Gonthier J. also stated that the duty involved reasonable diligence:
As a fiduciary, the DIA was required to act with reasonable diligence. In my view, a reasonable person in the DIA’s position would have realized by August 9, 1949 that an error had occurred, and would have exercised the s. 64 power to correct the error, reacquire the mineral rights, and effect a leasing arrangement for the benefit of the Band. That this was not done was a clear breach of the DIA’s fiduciary duty to deal with I.R. 172 according to the best interests of the Band.
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[138] At the time of the events in dispute in this Claim, Numukamis IR 1 was fully created in law. The further requirements are: to act in good faith and with full disclosure during the course of the trusteeship and management of the land comprising the HFN’s Reserve, and to protect and preserve the Reserve from exploitation. The Crown, in assuming this role is also required to act with “reasonable diligence” to the standard of “a man of ordinary prudence in managing his own affairs” (Blueberry River at paras 22, 104, citing Fales v Canada Permanent Trust Co, [1977] 2 SCR 302, at 315).
Link:
https://decisions.sct-trp.ca/sct/rod/en ... 3/index.do