There are two simple sentences at the beginning of Judge Vaughn Walker's opinion in Perry v. Schwarzenegger invaliding Proposition 8, which banned gay marriage in California: A state’s interest in an enactment must of course be secular in nature. The state does not have an interest in enforcing private moral or religious beliefs without an accompanying secular purpose. These sentences are crucial for understanding the appropriate role of religion in government and in the passage of legislation.
Plaintiffs challenged Proposition 8 as a violation of their Due Process and Equal Protection rights under the Fourteenth Amendment to the U.S. Constitution. A simple way to word these challenges is to say that the government must have a rational basis--some reason--whenever it passes legislation. Under Due Process, if the government denies a person the fundamental right to marry, it must have a compelling reason to do so. Under Equal Protection, if the government grants one person a marriage license but refuses a license to another, it must have some good reason for the distinction. A government allowed to act without reasons would be all-powerful and constantly violate individual rights.
Judge Walker's opinion was detailed and persuasive in explaining that the reasons favoring Proposition 8 were private moral and religious beliefs that were not the appropriate basis of civil law. He first described how Proposition 8 proponents abandoned previous arguments from the campaign that had asserted the moral superiority of opposite-sex couples. The rest of the opinion demonstrated the inadequacy of such moral arguments about gay marriage as the basis of legislation. The facts established at trial--demonstrated through the testimony of experts who had studied the history of marriage, compared gay marriage to heterosexual marriage and gay parents to heterosexual parents--demonstrated beyond serious reckoning that Proposition 8 finds support only in such [moral] disapproval. The idea that gay marriage was inferior to heterosexual marriage were not supported by any evidence offered by Proposition 8's proponents other than their religious and moral beliefs. As the opinion said at the beginning, however, personal moral and religious disapproval is not a secular purpose that can provide the basis for legislation. It is not a legitimate reason for the government to act.