O’REGAN J and SACHS J it. He supported his argument by referring to a series of Canadian cases, starting with Big M Drug Mart where Dickson CJC criticised the notion that a purpose could shift: “[T]he theory of a shifting purpose stands in stark contrast to fundamental notions developed in our law concerning the nature of ‘Parliamentary intention’. Purpose is a function of the intent of those who drafted and enacted the legislation at the time, and not of any shifting variable. .... While the effect of such legislation as the Lord’s Day Act may be more secular today than it was in 1677 or in 1906, such a finding cannot justify a conclusion that its purpose has similarly changed. In result, therefore, the Lord’s Day Act must be characterized as it has always been, a law the primary purpose of which is the compulsion of sabbatical observance.”64 In Butler,65 Sopinka J qualified the Court’s approach by stating that it is not necessary to resort to the “shifting purpose” doctrine to accept that if the objective of the statute was to prevent harm, then changing community values as to what was harmful could be taken into account in considering the constitutionality of a law. He observed that in proving that the original objective remained pressing and substantial, and that the measure was proportional, the government could draw on the best evidence currently available and rely 64 Above n 62 at 96-7. 65 Above n 60 at 31ff. 74