The term 'retrospective operation' is ambiguous because it is applied both to the fact that a particular enactment operates from before its date or so as to affect pre-existing rights and to the problem of construction which may be presented by an enactment as to whether it extends backwards or not. When an enactment extends backwards, by its own clear language, it operates retrospectively. It is only when the intention of the Legislature docs not lie on the surface that a question of interpretation arises and, in such a case, in deciding whether the enactment concerned is intended to operate retrospectively certain well-known principles are followed. ….. [Commissioner of Income Tax East Pakistan vs. Redhashyam Agarwalla (I960) 12 DLR I (PC)]
Retrospective operation ought not to be given to a statute, unless an intention to that effect is expressed in plain and unambiguous language. ….. [Young vs. Adams (1898) AC 469]