Crown Forest Industries Ltd. v. Canada, 95 DTC 5389, [1995] 2 SCR 802, [1995] 2 CTC 64 -- summary under Income Tax Conventions

Before referring to various extrinsic materials, Iacobucci J. stated (at p. 5396) that "reviewing the intentions of the drafters of a taxation convention is a very important element in delineating the scope of the application of that treaty" and "that, in ascertaining these goals and intentions, a court may refer to extrinsic materials which form part of the legal context (these include accepted model conventions and official commentaries thereon) without the need first to find an ambiguity before turning to such materials.