In the case of R v Big M Drug Mart, what principle was applied?

The principle applied in R v Big M Drug Mart is the pith and substance doctrine, which involves examining the main purpose and effect of a law to determine whether it falls within the jurisdiction of the government that enacted it. In this case, the Supreme Court of Canada focused on how the law, which prohibited certain business activities on Sundays, had an effect that was primarily directed at enforcing a particular religious practice, rather than serving a valid secular purpose.

By employing the pith and substance analysis, the Court recognized that the intent and underlying purpose of the law were to uphold a specific religious observance, which violated the freedom of religion guaranteed under section 2(a) of the Canadian Charter of Rights and Freedoms. The determination that the law's primary aim was to promote religious observance led to its invalidation, as it could not be justified in a manner consistent with Canada's commitment to pluralism and individual rights.

This case underscores the importance of assessing the true essence of laws rather than just their outer form or the effects they might have. The pith and substance doctrine serves as a crucial analytical tool in constitutional interpretation, particularly when determining whether a law aligns with fundamental rights and freedoms.