In a landmark decision announced October 18, the U.S. Court of Appeals for the Second Circuit struck down Section 3 of the Defense of Marriage Act (DOMA), which defines marriage as between one man and one woman for federal purposes. It is the second federal appeals court to rule that the law is unconstitutional (after the First Circuit’s ruling in Gill v. Office of Personnel Management), but it is the first to apply “intermediate scrutiny” in doing so. Including district court rulings, it is the tenth federal court in a row to strike down the Act as violating the Constitution’s Equal Protection Clause.

In the case, Windsor v. United States, Ms. Edith Windsor sued as the surviving spouse of a same-sex couple. The couple had been married in Canada, and they resided in New York until the other spouse’s death. Ms. Windsor was denied the benefit of a spousal deduction for federal estate taxes solely because of the federal definition of “spouse” under Section 3 of DOMA.

In this column, I will provide a short background on the different levels of scrutiny that arise from the Constitution’s Equal Protection Clause, and explain why the Second Circuit applied intermediate scrutiny in this case. Then I will describe the holding, putting it in context as compared to other DOMA cases, and suggesting how together such cases may set the stage for the U.S. Supreme Court to decide the matter.

The Relevant Classifications and Levels of Judicial Scrutiny

Most notably, in Windsor v. United States, the majority expressly held that classifications based on sexual orientation should receive a heightened level of scrutiny, often termed “intermediate scrutiny.” It was the first court to make such a determination without also assessing the constitutionality of the law under a lower level of scrutiny. Applying this heightened scrutiny, the Second Circuit majority found Section 3 of DOMA unconstitutional.

“Intermediate scrutiny” refers to a level of review that courts apply when determining whether a particular law violates the Constitution’s Equal Protection Clause. Nearly all laws classify people into groups, but the Constitution places restrictions on the ways in which these classifications may operate.

Certain types of classifications are “suspect” and receive the highest level of judicial scrutiny: strict scrutiny. Among such suspect classifications are those based on race, national origin, religion, or alienage. Classifications that burden a fundamental right—such as the right to vote, the right of interstate migration, or the right of access to the courts—are also suspect, and laws employing such classifications are subject to strict scrutiny, as well. Strict scrutiny requires that the government show that the challenged classification serves a compelling government interest, and that the classification is necessary to serve that interest. In practice, the application of strict scrutiny nearly always results in the invalidation of the law at issue.

Courts apply a second, less stringent level of scrutiny to laws that classify persons on the basis of gender or illegitimacy, or other “quasi-suspect” classifications. The Supreme Court established a set of factors to determine whether a new classification is quasi-suspect for the purpose of this level of review:

Whether the affected class has historically been subjected to discrimination; Whether the class has a defining characteristic that affects its ability to contribute to society; Whether the class exhibits obvious or immutable characteristics that define them as a discrete group; and Whether the class is politically powerless.

These four factors are taken together as a whole to determine whether a classification is quasi-suspect, and the presence or absence of any one factor is not dispositive. Laws that discriminate on the basis of a quasi-suspect class are subject to heightened (or intermediate) scrutiny, which requires that the classification be substantially related to an important government interest.

The lowest level of scrutiny—rational basis scrutiny—applies to all other types of classifications, and requires only that the government show that the classification is rationally related to a legitimate state interest.

The Appropriate Level of Scrutiny for Classifications Based on Sexual Orientation

The appropriate level of scrutiny for classifications based on sexual orientation has been a contested issue in courts across the country.

In one early case, decided in 1990, High Tech Gays v. Defense Industrial Security Clearance Office, the U.S. Court of Appeals for the Ninth Circuit ruled that sexual orientation was not subject to heightened scrutiny, so laws that classify on that basis are subject only to the rational basis test. The court’s reasoning in that case was based on the Supreme Court’s decision in Bowers v. Hardwick, in which the Court had held that “homosexual activity is not a fundamental right protected by substantive due process and the proper standard of review under the Fifth Amendment is rational basis review.” That case remained the law in the Ninth Circuit and also constituted persuasive authority nationwide, until it was gutted by the Supreme Court’s 2003 decision in Lawrence v. Texas, which I discuss below.

In the watershed case Romer v. Evans, decided in 1996, the U.S. Supreme Court ruled that an amendment to the state constitution of Colorado violated the federal Constitution’s equal protection guarantee because it singled out individuals on the basis of a single trait—sexual orientation—and denied only that specific group protection from discrimination. Applying the rational basis test, the Court held that such a classification bore no rational relationship to any legitimate government interest. The Court did not need to rule on whether heightened scrutiny was appropriate (and, indeed, did not rule on the issue) because the proposed amendment could not even pass the lowest level of scrutiny, as it lacked even a rational basis.

In 2003, the U.S. Supreme Court held in Lawrence v. Texas that the government has no legitimate interest in regulating—let alone criminalizing—consensual conduct between two adults that occurs in private. The decision expressly overruled Bowers, and in doing so, invalidated the body of laws that had relied upon the holding in Bowers, including High Tech Gays. The decisions were surely the right ones, but after they were handed down, the question of what is the appropriate level of scrutiny for laws classifying individuals based on sexual orientation was once again unsettled.

A series of recent lower-court cases, including a bankruptcy court ruling, have strongly suggested that heightened scrutiny is the appropriate level for these types of classifications. In Golinski v. Office of Personnel Management, Judge Jeffrey White of the U.S. District Court for the Northern District of California ruled that DOMA was unconstitutional under both intermediate scrutiny and the rational basis test. In Gill v. Office of Personnel Management, the U.S. Court of Appeals for the First Circuit held that Section 3 of DOMA could not survive the rational basis test, but did not address whether a heightened level of scrutiny was appropriate. Finally, in Windsor v. United States, the case decided last week, the U.S. Court of Appeals for the Second Circuit unequivocally held that classifications based on sexual orientation are subject to heightened scrutiny and that under this level of scrutiny, DOMA cannot stand.

Setting the Stage for Supreme Court Review

Among the many cases challenging the constitutionality of DOMA, five are the subject of certiorari petitions. Four of the five are based on equal protection challenges:

Gill v. Office of Personnel Management (appeals court applying rational basis test only)

Pedersen v. Office of Personnel Management (district court applying rational basis test only)

Golinski v. Office of Personnel Management (district court applying heightened scrutiny and rational basis test)

Windsor v. United States (appeals court applying heightened scrutiny only)

A fifth case, Hollingsworth v. Perry, is also pending, but that case does not involve DOMA directly; rather, it challenges a state constitutional amendment purporting to define marriage in California as being exclusively between one man and one woman. However, the resolution in this fifth case could determine how the DOMA cases will be decided.

Despite the fact that several courts, including a federal appeals court, have ruled that DOMA cannot pass even the least stringent rational basis test, commentators have suggested that the Supreme Court might split on that issue, with the ultimate result difficult to predict.

The Windsor case is significant, however, for if the Supreme Court accepts its holding that classifications based on sexual orientation merit heightened scrutiny, then the Court is much more likely to strike down DOMA using that more demanding test. Based on the language of the opinion in Windsor and the meticulousness with which the Windsor majority addresses the requirements for identifying whether a class of individuals is quasi-suspect for equal protection purposes, it seems eminently plausible that the Supreme Court will accept the application of heightened scrutiny to DOMA and other laws that classify on the basis of sexual orientation.

In conjunction with the case challenging California’s Proposition 8—where the U.S. Court of Appeals for the Ninth Circuit held unconstitutional a state constitutional amendment purporting to define marriage in California as between one man and one woman—the cases that I have described above all but guarantee that the Supreme Court will take up the issue.