Why did Reynolds v. United States allow the government to prohibit polygamy despite religious beliefs?

In Reynolds v. United States (1879), the U.S. Supreme Court upheld the government's power to prohibit polygamy, ruling that the First Amendment's protection of the free exercise of religion does not grant individuals the right to engage in practices that are otherwise illegal under federal law.12

The Court established a critical distinction between religious belief and religious conduct. While the government cannot interfere with an individual's freedom to hold religious beliefs, it maintains the authority to regulate actions that are deemed socially harmful or contrary to established law. By upholding the Morrill Anti-bigamy Act of 1862, the Court affirmed that religious conviction does not provide a legal exemption from laws designed to protect the social order and public morality. This decision set a significant precedent, establishing that the exercise of religion is not absolute when it conflicts with the government's interest in maintaining civil order.12