Gender, the gay marriage fight's missing piece: Column Bans on same-sex unions are illegal because they discriminate against men & women, not gays.

Andrew Koppelman and Ilya Somin | USATODAY

As the Supreme Court considers the constitutionality of laws banning same-sex marriage later this month, few have noticed that the case can easily be resolved under existing precedent.

Laws banning gay marriage are unconstitutional because they discriminate on the basis of gender. If same-sex marriage is forbidden, Anne is allowed to marry Bob, but Charles can't. Charles is denied the right to marry Bob, solely because Charles is a man. Denial of a legal right solely because of gender is the very essence of sex discrimination.

Laws banning gay marriage discriminate on the basis of gender even more clearly than on the basis of sexual orientation. Anne is still allowed to marry Charles, even if one of them happens to be gay or lesbian. Bob is denied that right whether he is gay or not. The Supreme Court has long held that laws discriminating based on gender must be presumed unconstitutional and invalidated unless the government can prove that they can pass rigorous, heightened judicial scrutiny.

Some lower court decisions have ruled that laws banning gay marriage do not discriminate on the basis of sex because they affect members of both genders equally: Men are forbidden to marry other men, and women are forbidden to marry other women. But this is exactly the same kind of reasoning that the Supreme Court rejected when it struck down laws banning miscegenation and interracial marriage. The defenders of those laws claimed that they did not discriminate on the basis of race because both blacks and whites were equally barred from marrying members of the other racial group.

Just as a law banning interracial marriage discriminates on the basis of race, so a law banning same-sex marriage discriminates on the basis of gender. It still denies rights to both men and women solely on account of their sex. The fact that Bob cannot marry Charles solely on account of gender is not somehow balanced by the fact that Anne is forbidden to marry Carol.

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Other critics of the gender discrimination argument claim that laws banning gay marriage do not discriminate on the basis of sex because they are not motivated by sexist prejudice. But the Supreme Court has repeatedly ruled that laws restricting individuals' rights on the basis of their gender qualify as sex discrimination regardless of motivation. Craig v. Boren, the 1976 case in which the Supreme Court first ruled that gender discrimination is subject to heightened scrutiny, invalidated an Oklahoma law under which 18- to 20-year-old men, but not women of the same age, were forbidden to buy beer. The Oklahoma legislature was not rife with anti-male sexism.

Many opponents of gay marriage rely in part on gender stereotypes. Some judges who have rejected same-sex marriage have claimed that opposite-sex marriage is essential to prevent men (but not women) from procreating irresponsibly and disclaiming responsibility for their children, or because children must have role models of the same sex, or that the presence of parents of both genders is essential to optimal child raising, even though social scientific evidence cuts against such claims. The Supreme Court has ruled that laws may not be based on "fixed notions concerning the roles and abilities of males and females." Even in cases where such stereotypical notions have some statistical validity, the government may not engage in systematic gender discrimination on that basis — penalizing all those who wish to enter into gay marriages based on the possible shortcomings of a minority.

Some defenders of same-sex marriage fear that the gender discrimination argument ignores what they see as the true motivation for the laws they oppose: prejudice against gay men and lesbians. But hostility to gays and lesbians and sexism are often closely linked. At least until recently, most Americans learned no later than high school that one of the nastier social sanctions one will suffer for deviating from traditional gender roles is the imputation of homosexuality. Much anti-homosexual prejudice is closely linked to gays' and lesbians' supposed deviation from conventional gender norms. While gay men are often stigmatized for being "effeminate," lesbians are stereotyped as too masculine.

Not all opposition to same-sex marriage is rooted in sexism. But such factors are prominent enough that the gender discrimination rationale for striking down laws banning gay marriage cannot be dismissed as mere legal formalism.

The two of us have very different political views and approaches to constitutional interpretation. Even so, we are united on this case; people with widely differing views on other issues can recognize that laws banning same-sex marriage discriminate on the basis of gender, and therefore should be subject to the same constitutional rules as other laws that enforce sex discrimination.

Andrew Koppelman, a professor of law at Northwestern University, and Ilya Somin, a law professor at George Mason University are co-authors of an amicus brief urging the Supreme Court to invalidate laws banning same-sex marriage.

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