U.S. District Judge Vaughn Walker's decision overturning Proposition 8, California's gay marriage ban, rests on two constitutional arguments—a due process claim and an equal protection claim—that raise essentially the same question: Do homosexual marriages differ from heterosexual marriages in a way that should matter to the government? Defenders and opponents of Proposition 8 agreed that the freedom to marry is a "fundamental right" protected by the 14th Amendment's Due Process Clause (more plausibly, it's protected by the Privileges or Immunities Clause, but that's an argument for another day). "The question presented here," Walker writes, "is whether plaintiffs seek to exercise the fundamental right to marry; or, because they are couples of the same sex, whether they seek recognition of a new right." Likewise, the equal protection claim hinges on the question of whether gay and straight couples are "similarly situated" and whether there is a "rational basis" for treating them differently. Examining the evidence presented during the trial, Walker concludes that the two kinds of couples are identical with respect to any legitimate state interest:
During cross-examination, [David] Blankenhorn [an expert witness who testified in defense of Prop. 8] was shown a report produced by his Institute in 2000 explaining the six dimensions of marriage: (1) legal contract; (2) financial partnership; (3) sacred promise; (4) sexual union; (5) personal bond; and (6) family-making bond. Blankenhorn agreed that same-sex marriages and opposite-sex marriages would be identical across these six dimensions….Children raised by gay or lesbian parents are as likely as children raised by heterosexual parents to be healthy, successful and well-adjusted….Same-sex couples are identical to opposite-sex couples in the characteristics relevant to the ability to form successful marital unions….Same-sex couples are situated identically to opposite-sex couples in terms of their ability to perform the rights and obligations of marriage under California law.
Walker also argues that the right to marry was not transformed when courts overturned anti-miscegenation laws or when the law began to treat men and women as equal partners. Likewise, he says, the right to marry is not transformed by allowing gay couples to exercise it:
The movement of marriage away from a gendered institution and toward an institution free from state-mandated gender roles reflects an evolution in the understanding of gender rather than a change in marriage. The evidence did not show any historical purpose for excluding same-sex couples from marriage, as states have never required spouses to have an ability or willingness to procreate in order to marry. Rather, the exclusion exists as an artifact of a time when the genders were seen as having distinct roles in society and in marriage. That time has passed. The right to marry has been historically and remains the right to choose a spouse and, with mutual consent, join together and form a household. Race and gender restrictions shaped marriage during eras of race and gender inequality, but such restrictions were never part of the historical core of the institution of marriage.
Prop. 8's defenders obviously disagree about what lies at the core of marriage. But they did a poor job of explaining why the government should enforce their view. To the extent that the state has good reasons for distinguishing between married and single people, Walker is right that they apply to gay couples as much as they apply to straight couples.