In a case in Nevada whereby the US Circuit Court upheld traditional marriage, District Judge Robert Jones wrote,
“Although the distinction the State has drawn (between one-man–-one-woman marriages on the one hand, and any other gender- or number-configuration of spouses on the other hand) largely burdens homosexuals, the distinction is not by its own terms drawn according to sexual orientation. Homosexual persons may marry in Nevada, but like heterosexual persons, they may not marry members of the same sex. That is, a homosexual man may marry anyone a heterosexual man may marry, and a homosexual woman may marry anyone a heterosexual woman may marry. In this sense, the State of Nevada has drawn no distinction at all. Under this conception of the (lack of) distinction drawn by the State, the laws at issue would receive no scrutiny at all under the Equal Protection Clause.”
“As Justice O’Connor noted in concurrence in Lawrence, there are additional reasons to promote the traditional institution of marriage apart from mere moral disapproval of homosexual behavior, and these reasons provide a rational basis for distinguishing between opposite-sex and same-sex couples in the context of civil marriage.
Human beings are created through the conjugation of one man and one woman. The percentage of human beings conceived through non-traditional methods is minuscule, and adoption, the form of child-rearing in which same-sex couples may typically participate together, is not an alternative means of creating children, but rather a social backstop for when traditional biological families fail. The perpetuation of the human race depends upon traditional procreation between men and women. The institution developed in our society, its predecessor societies, and by nearly all societies on Earth throughout history to solidify, standardize, and legalize the relationship between a man, a woman, and their offspring, is civil marriage between one man and one woman.
( “It is an institution, in the maintenance of which in its purity the public is deeply interested, for it is the foundation of the family and of society, without which there would be neither civilization nor progress.” - See Maynard v. Hill, 125 U.S. 190,211 (1888) )
“Should that institution be expanded to include same-sex couples with the state’s imprimatur, it is conceivable that a meaningful percentage of heterosexual persons would cease to value the civil institution as highly as they previously had and hence enter into it less frequently, opting for purely private ceremonies, if any, whether religious or secular, but in any case without civil sanction, because they no longer wish to be associated with the civil institution as redefined, leading to an increased percentage of out-of-wedlock children, single-parent families, difficulties in property disputes after the dissolution of what amount to common law marriages in a state where such marriages are not recognized, or other unforeseen consequences.
Because the family is the basic societal unit, the State could have validly reasoned that the consequences of altering the traditional definition of civil marriage could be severe. It is not beyond rational speculation to conclude that fundamentally altering the definition of marriage to include same-sex unions might result in undermining the societal understanding of the link between marriage, procreation, and family structure.”
HT: email from Micah Clark, AFAIN