Courts have long frowned on the practice of raising new arguments on appeal. The concerns are two-fold: first, prejudice to the other side caused by the lack of opportunity to respond and adduce evidence at trial and second, the lack of a sufficient record upon which to make the findings of fact necessary to properly rule on the new issue.
See Chuang v. Toyota Canada Inc., 2016 ONCA 852; College of Optometrists of Ontario v. SHS Optical Ltd. (c.o.b. Great Glasses), 2008 ONCA 6895 (CanLII); Kaiman v. Graham, 2009 ONCA 77 (CanLII), 245 O.A.C. 130, at para. 18
A party seeking to re-open an appeal after the appeal decision has been rendered faces a high hurdle.. In Mujagic v. Kamps, 2015 ONCA 360 (2015 ONCA 360 (CanLII), 125 O.R. (3d) 715, at para. 12, the Court of Appeal for Ontario said that the power to re-open an appeal “will be exercised sparingly and only where it is clearly in the interests of justice”.