In what circumstances will legislation be expressly retroactive?

Counsel then made submissions respecting the necessity of legislation being expressly retroactive. He referred to MacKenzie v. B.C., 1992 D.L.R. (4th) 532 in which Wood, J.A. at 537 said: ... in the absence of express words to the contrary, or a necessary and distinct implication arising from the construction of the statute as a whole, an amendment is presumed not to have retroactive effect. That is a presumption of law, and the onus is on the appellant [in this case the appellant propounded the retroactivity of the legislation in question] to demonstrate the probability that the amendment in question was intended by the legislature to have such an effect.