Régie des rentes du Québec v. Canada Bread Co.,  3 S.C.R.
125,  S.C.J. No. 46, 2013 SCC 46, at para. 28.
 In Régie des rentes du Québec, the court described the
operation of retroactive legislation, at paras. 26-28:
It is settled law in Canada that it is within the prerogative of the legislature to
enter the domain of the courts and offer a binding interpretation of its own law
by enacting declaratory legislation: L.-P. Pigeon, Drafting and Interpreting
Legislation (1988), at pp. 81-82. As this Court acknowledged in Western
Minerals Ltd. v. Gaumont,  1 S.C.R. 345, such forays are usually made
where the legislature wishes to correct judicial interpretations that it perceives
to be erroneous.
In enacting declaratory legislation, the legislature assumes the role of a court
and dictates the interpretation of its own law: P.-A. Côté, in collaboration with
S. Beaulac and M. Devinat, The Interpretation of Legislation in Canada (4th ed.
2011), at p. 562. As a result, declaratory provisions operate less as legislation
and more as jurisprudence. They are akin to binding precedents, such as the
decision of a court: P. Roubier, Le droit transitoire: conflits des lois dans le temps
(2nd ed. 1993), at p. 248. Such legislation may overrule a court decision in the
same way that a decision of this Court would take precedence over a previous
line of lower court judgments on a given question of law.
It is also settled law that declaratory provisions have an immediate effect on
pending cases, and are therefore an exception to the general rule that legislation is prospective. The interpretation imposed by a declaratory provision
stretches back in time to the date when the legislation it purports to interpret
first came into force, with the effect that the legislation in question is deemed
to have always included this provision. Thus, the interpretation so declared is
taken to have always been the law: R. Sullivan, Sullivan on the Construction
of Statutes (5th ed. 2008), at pp. 682-83.
(Citations in original)
 The appellants argue that the respondents should not be
able to take advantage of the regulated conduct defence when
the conduct in issue is retroactively sanctioned. I do not agree. The
purpose of extending that defence in the context of the Competition
Act is to avoid criminalizing conduct that a province deems to be in
the public interest. That same provincial public interest should be
recognized whether it is expressed in legislation in force at the time
of the impugned acts, or expressed in retroactive legislation.
Further, there is no logical basis to treat Brewers Retail Inc. differently from the LCBO with respect to the market allocation agreement. They are opposite sides of the same transaction which
benefits from the regulated conduct defence.
(2) The price differential for beer sales to consumers and
 As I have indicated above, the appellants allege that the
5 per cent surcharge Brewers Retail Inc. levied on licensees, as
compared to consumers, violated the Liquor Control Act, as it