R. v. Big M Drug Mart Ltd. is a landmark Supreme Court of Canada decision from 1985 that dealt with the constitutionality of the Lord's Day Act, which mandated Sunday as a day of rest and prohibited businesses from operating on that day. This case highlighted the importance of balancing majority societal values with the rights of minority groups, specifically religious minorities, in a pluralistic society. The ruling emphasized that laws should respect individual freedoms and not impose religious beliefs on those who do not adhere to them.