In the case of McGowan et al. v. Maryland, the US Supreme Court upheld a Maryland statute that prohibited commercial activities on Sunday, rejecting claims that it violated religious freedom rights protected by the First Amendment. The appellants were employees of a large discount department store who had been convicted for selling merchandise on Sunday in violation of this law. They argued that these laws established a state religion and infringed upon their personal liberties as they originated from Christian practices and beliefs about observing Sundays as days of rest or Sabbath days. However, the court ruled 8-1 in favor of Maryland stating that while such laws may have originally been motivated by religious concerns, they now served important secular purposes like providing a uniform day off work for all citizens regardless if one was religious or not.

In the dissenting opinion for McGowan et al. v. Maryland, Justice William O. Douglas argued that the state's Sunday closing laws were a violation of the First Amendment's Establishment Clause because they represented an endorsement of Christianity by giving preference to its day of worship over other religions'. He contended that these laws forced non-Christian businesses and consumers to conform to Christian practices, thereby infringing upon their religious freedom. Furthermore, he rejected the majority’s view that these laws had become secular in nature due to their long history and widespread acceptance; instead, he maintained that their origins in religious observance could not be divorced from their current application regardless of any purported secular purpose or effect.