Standard Classification-Based Equal Protection
The second argument dominating litigation today is that a same-sex marriage ban discriminates on the basis of sexual orientation in violation of the Equal Protection Clause or similar state constitutional provisions. In general, courts defer to judgments by legislatures about what laws should be made. But to make sure that the state does not unfairly discriminate, courts look carefully at laws that single out individuals on the basis of race, sex, religion, or alienage. In cases seeking to expand marriage rights, advocates have argued that laws that make distinctions on the basis of sexual orientation should likewise trigger such heightened scrutiny (or, in legal parlance, they claim that sexual orientation should be considered a “suspect classification”). Where they have been able to convince state courts to apply heightened scrutiny, same-sex couples have won the right to marry, or at least the right to an equivalent legal status. In fact, no state court that has applied any form of heightened equal protection review has upheld a different-sex marriage requirement.
However, courts in several states have held that classifications on the basis of sexual orientation do not raise special concerns and therefore do not prompt any presumption of invalidity. Courts in New York, Washington, Maryland, Indiana, and Arizona have all upheld different-sex marriage laws under ordinary scrutiny, as have several lower federal courts. While the highest court in Massachusetts did strike down a ban on same-sex marriage under ordinary review,3 it does not seem to have inspired a trend in that direction.
We agree that bans on same-sex marriage should be held to violate the standard conception of equal protection. But there is a widespread sense that the Supreme Court is unlikely to announce that classifications on the basis of sexual orientation are always suspect. Indeed, the Court may be moving away from the tiers of scrutiny framework altogether. As a practical matter, therefore, a classification-based equal protection argument is not likely to succeed in federal court or in many state courts.