evidence is always available to interpret historical treaties. Mackinnon A.C.J.O.
stated in Taylor and Williams, “if there is evidence by conduct or otherwise as to
how the parties understood the terms of the treaty, then such understanding and
practice is of assistance in giving content to the term or terms.”60 He accepted the
common submission of counsel before him that “recourse could be had to the
surrounding circumstances and judicial notice could be taken of the facts of
history.”61 He added: “In my opinion, that notice extends to how, historically, the
parties acted under the treaty after its execution.”62 The court need not find an
ambiguity in a treaty before admitting extrinsic evidence.63
 Binnie J. explained in Marshall:
The special rules are dictated by the special difficulties of
ascertaining what in fact was agreed to [in historical
treaties]. The Indian parties did not, for all practical
purposes, have the opportunity to create their own written
record of the negotiations. Certain assumptions are
therefore made about the Crown’s approach to treaty
making (honourable) which the Court acts upon in its
approach to treaty interpretation (flexible) as to the
existence of a treaty, the completeness of any written
record (the use, e.g., of context and implied terms to
make honourable sense of the treaty arrangement, and
the interpretation of treaty terms once found to exist.64
60 R. v. Taylor and Williams (1981), 62 C.C.C. (2d) 227 (Ont. C.A.), at p. 236, per MacKinnon A.C.J.O.,
leave to appeal refused,  2 S.C.R. xi.
61 Taylor and Williams, at p. 236.
62 Taylor and Williams, at p. 236.
63 Marshall, at para. 11, per Binnie J. The Supreme Court has approved the approach in Taylor and
Williams on many occasions and has never doubted it: see e.g., Marshall; Sioui; R. v. Sparrow,  1
S.C.R. 1075; and Delgamuukw v. British Columbia,  3 S.C.R. 1010.
64 Marshall, at para. 14, per Binnie J. (citations omitted).