R v Ewanchuc, 1999 SCJ 10 (Major):

[51] For instance, a belief that silence, passivity or ambiguous conduct constitutes consent is a mistake of law, and provides no defence: see R. v. M. (M.L.), [1994] 2 S.C.R. 3. Similarly, an accused cannot rely upon his purported belief that the complainant’s expressed lack of agreement to sexual touching in fact constituted an invitation to more persistent or aggressive contact. An accused cannot say that he thought “no meant yes”.