The Equal Protection Clause is one of the most litigated and significant provisions in contemporary constitutional law. The meaning of the clause is bound up with the entire drama of the Civil War and Reconstruction and, in particular, with slavery and emancipation. Thus, the Equal Protection Clause can be understood only as an organic part of the Fourteenth Amendment and in the broader context of all the Reconstruction amendments.

Debate on the original understanding of the Equal Protection Clause became intense in modern times after the Supreme Court ordered briefing and re-argument on the question in Brown v. Board of Education (1954), the school desegregation case. Scholarly debate on the original intention of the Equal Protection Clause and, more broadly, on Section 1 of the Fourteenth Amendment, continues to the present day. Controversy centers on two primary questions. The first is how far, or in relation to what rights, did the framers of the amendment intend the command of equality to apply? In other words, equal as to what? The second is what does it mean to treat persons equally? In other words, what is equal treatment?

Under current Supreme Court doctrine, the scope of equal protection is as broad as governmental action under the State Action doctrine. The command to treat persons equally extends to all actions by the government. Most commentators agree, however, that the intended scope of the Equal Protection Clause was not as broad.

The framers of the Fourteenth Amendment focused primarily on the status of the freed slaves, and debated the command of equal protection primarily in racial terms. Congress had enacted the Civil Rights Act of 1866 largely in response to perceived Southern oppression of the freed slaves, particularly in the form of “Black Codes” enacted in the former Confederate states. John A. Bingham, the primary author of Section 1 of the Fourteenth Amendment, did not believe that Congress had the constitutional authority to enact the Civil Rights Act of 1866, and he therefore intended to provide congressional authority for that enactment by constitutional amendment. When Bingham’s version of Section 1 emerged from committee for consideration by the full Congress, it was received primarily as a means of legitimizing the 1866 Civil Rights Act. At a minimum, the framers intended that the command of equal protection apply to the rights protected by the Civil Rights Act of 1866, which provided for the “same right”:

[T]o make and enforce contracts, to sue, be parties, and give evidence, to inherit, purchase, lease, sell, hold, and convey real and personal property, and to full and equal benefit of all laws and proceedings for the security of person and property . . . and shall be subject to like punishment, pains, and penalties, and to none other. . . .

The methodology of the first section of the Civil Rights Act was to define national citizenship and to declare that all citizens, “of every race and color,” should have the same benefit of the listed rights “as is enjoyed by white citizens.” The language of Section 1 of the Fourteenth Amendment, by contrast, can be read to distinguish between citizenship rights protected by the Privileges or Immunities Clause and personhood rights protected by the Due Process and Equal Protection Clauses. Once the Supreme Court gutted the Privileges or Immunities Clause of the Fourteenth Amendment in The Slaughter-House Cases, the Equal Protection Clause became the primary bulwark supporting the constitutionality of the Civil Rights Act and providing for the enforcement of its listed rights.

The framers’ jurisprudence tended to lump together rights flowing from citizenship and personhood under the rubric of “civil rights,” and to speak of them in religious or natural law and natural rights terms. In Section 1 of the Fourteenth Amendment, the framers attempted to create a legal bridge between their understanding of the Declaration of Independence, with its declarations of universal equality and rights endowed by a Creator God, and constitutional jurisprudence. However, the framers also prized federalism—although not in the absolutist sense of the Southern secessionists. Antislavery activists themselves had at times relied on state authority to resist federal policies protective of slavery and so shared that era’s common mistrust of centralized authority. The Fourteenth Amendment’s compromise between federal enforcement of civil rights and the maintenance of significant state authority has remained in tension since the amendment’s ratification.

The rhetoric of the time distinguished civil equality from two other kinds of possible equality: political and social. The framers of the Fourteenth Amendment chose not to include political rights (such as the right to vote, which the Fifteenth Amendment would later address) and social rights within the protections of the Fourteenth Amendment. The Fourteenth Amendment, including its then more prominent sections regarding representation and the political exclusion of certain former Confederates, was part of the Republican Party’s Reconstruction program during the critical 1866 election. The program was popular because of its perceived moderation by Northern opinion of the time, which was generally negative or ambivalent in regard to political and social equality for African-Americans. After achieving political success in the 1866 election, Republicans became bolder, enacting the Fifteenth Amendment, explicitly protecting the right to vote. However, the very passage of the Fifteenth Amendment indicates that voting rights were insufficiently protected by the Fourteenth Amendment.

The Equal Protection Clause burst into new prominence in the mid-twentieth century with the Court’s decision in Brown v. Board of Education, invalidating segregated public education and signaling the end of the “separate but equal” doctrine of Plessy v. Ferguson (1896). The question of whether Brown was consonant with the original intent of the framers of the clause is the subject of much debate. Some scholars view the provision (and integration) of education as local, social, or political in nature, and hence as beyond the original scope of the Fourteenth Amendment. Others would point to post-1866 Republican efforts to desegregate schools as evidence that Brown is a plausible interpretation of the framers’ intent. Antislavery rhetoric had been critical of Southern laws that outlawed basic education for slaves, and thus provision of education for the freed slaves would have been important to the framers. Arguably, then, education was neither a political nor a social right, but rather was related to a person’s right to the pursuit of happiness, or was a right equipping citizens for their civic responsibilities.

Even if the framers had viewed public accommodations and education as local or social rights not directly protected by the Equal Protection Clause, their sense of racial justice would have opposed the systematic, legally enforced racial caste system that emerged in the 1890s. In fact, in the so-called Ku Klux Klan Act (1871), Congress did attempt to thwart the violent racism that was the harbinger of Jim Crow. In any event, by the time segregation swept the South, it was part of the Jim Crow program to reduce blacks to a status not unlike that imposed by the “Black Codes,” which the Fourteenth Amendment was clearly intended to efface. The framers undoubtedly would have recognized that government and private institutions had coalesced to enforce a racial caste system that oppressed African-Americans in a manner inconsistent with the fundamental principle of civil equality. As Justice John M. Harlan famously declared in his dissent in Plessy v. Ferguson, “In view of the Constitution, in the eye of the law, there is in this country no superior, dominant, ruling class of citizens. There is no caste here.” The comprehensiveness of the racial caste system developed under Jim Crow made the original distinctions between civil, political, and social equality irrelevant, justifying the Court’s broad interpretation of the Equal Protection Clause in racial areas as necessary in order to effectuate the clause’s comprehensive guarantee of the “equal protection of the laws.”

During the era of “separate but equal” jurisprudence, the application of the clause to laws that discriminated on the basis of race was severely, although not entirely, eliminated. At the same time the Court had found the clause applicable to little else beyond race. Although the Equal Protection Clause textually restricted only the states, the principle behind it was also applied to the federal government in Korematsu v. United States (1944). Even though the Court used heightened scrutiny when it reviewed governmental action that discriminated against any race, not just African-Americans, the Court did not deem the principle sufficient to stop the internment of Japanese-Americans during World War II. With the clause generally ineffective as to racial matters and applicable to little else, the Equal Protection Clause became, in Justice Oliver Wendell Holmes’s words, the “usual last resort of constitutional arguments . . . .” Buck v. Bell (1927).

After the Court resurrected the Equal Protection Clause in regard to racial classifications, it was inevitable that questions would arise as to how the clause would be applied to nonracial classifications. While the history of the clause is focused on race, the language is after all general. This presents a conceptual and practical problem: All laws classify, and all laws make distinctions, leading to a virtually unlimited number of potential Equal Protection challenges. Close judicial review of all classifications to ensure “equal protection of the laws” is a practical impossibility. Although the clause protects all persons, the Court, as a practical matter, cannot give close scrutiny to all classifications that governmental action may create among persons.

Thus, the modern Court developed a two-tiered system of review: (1) strict scrutiny and (2) rational basis. All classifications based on race were subjected to “strict judicial review,” and they were thus subjected to a means-end test: the classification must be narrowly tailored to effectuate a compelling governmental interest. The Court determined which governmental interests (ends) were significant enough to be “compelling.” As a practical matter, in many cases the government could at least claim to be implementing an end or purpose deemed compelling under the Court’s precedents. Therefore the heart of strict scrutiny often rests in the means test.

Means-end testing involves essentially two questions: First, does the governmental action work, meaning does the governmental action actually serve the claimed interest? Second, if it does work, is there an alternative and less “suspect” (i.e., nonracial) classification that would work approximately as well, making use of the racial classification unnecessary to achievement of this goal? Under strict scrutiny, means-end testing involves a kind of public policy “second-guessing” of the legislative branch by the courts. By contrast, non-suspect classifications are presumptively constitutional, and they are therefore reviewed under the very lenient rational basis test, which asks whether the classification is rationally related to a legitimate government interest. Under rational basis review there is generally little second-guessing as to whether the law works, and the analysis of alternatives is irrelevant. The burden is on the complaining party to show that the only purpose of the legislation was entirely arbitrary, irrational, or invidiously discriminatory. See Railway Express Agency, Inc. v. New York (1949). Rational basis review has understandably developed into a virtual rubber stamp.

The group of classifications subject to strict scrutiny is very limited: race and its corollaries, such as national origin or ethnic group, and legal alienage, except where the classification is either created by the federal government (which has plenary control over immigration) or excludes aliens from political functions “intimately related to the process of democratic self-government,” such as serving as police and probation officers or public school teachers. Alienage classifications operating within the two exceptions are generally reviewed under the lenient rational basis test. Laws that classify based on religion are also subject to strict scrutiny, but that is typically done under the Religion Clauses of the First Amendment.

Beginning in the 1970s, the Court developed a third, intermediate standard of review for two classifications: sex and legitimacy (the distinction between marital and nonmarital children). The test for intermediary scrutiny asks whether the law is substantially related to an important government interest. As to sex, a number of decisions have emphasized that there must be “an exceedingly persuasive justification” for any sex classification. United States v. Virginia (1996). Although some interpret this language as implying a creep toward strict scrutiny for sex classifications, officially sex remains subject to intermediary scrutiny.

The Supreme Court has thus far refused to extend “heightened” scrutiny (that is, either strict or intermediary scrutiny) to any other classifications, even though some, such as age, disability, and sexual orientation, are frequently included in antidiscrimination legislation. The Court’s occasional decision to invalidate laws employing sensitive classifications, purportedly under the rational basis test, as in City of Cleburne v. Cleburne Living Center, Inc. (1985) (mental retardation) and Romer v. Evans (1996) (sexual orientation), underscores the Court’s reluctance to expand the classifications officially subject to heightened scrutiny. In fact a majority of the Court thus far prefers to rest the protection of same-sex relationships on the basis of due process rather than on equal protection. Lawrence v. Texas (2003).

The methodology by which the Court determines which classifications receive heightened scrutiny, beyond that of race, is unclear. Commentators have invoked the classification of “discrete and insular minorities” from the famous footnote four of United States v. Carolene Products Co. (1938), but the relevance of that footnote in modern times is hardly certain. Women, for example, are neither minorities nor insular. Justices and commentators have sometimes compared the historical discrimination experienced by African-Americans to that experienced by women, the mentally retarded, the poor, and those with a same-sex sexual orientation, but it is unclear whether there is commensurable scale for measuring tragic histories. In addition, once a classification is made suspect, under current precedents the Court will protect members of the historically favored, as well as historically disfavored, group. For example, the equal protection cases protect “sex,” not the female sex. Thus, the Court has invalidated a law that limited a nursing school to women, Mississippi University for Women v. Hogan (1982), and a law that allowed women, but not men, to buy alcohol at age 18, Craig v. Boren (1976). Given these difficulties, the Court has not yet developed a single methodology for determining the critical question of which classifications receive heightened scrutiny, nor for choosing between strict and intermediary scrutiny.

The question of affirmative action has spawned much litigation. Under current precedents, all legislative racial classifications are evaluated under strict scrutiny, even if they purport to be positive affirmative action programs favoring racial minorities. Although the primary impetus behind the Fourteenth Amendment (and its Equal Protection Clause) was to protect African-Americans, the framers of the amendment, as noted above, phrased the protection in general terms, and the courts have applied it in that fashion. Thus today, even classifications favoring African-Americans are presumptively unconstitutional absent sufficiently weighty reasons. The courts have held that the protection of all races against discrimination effectuates the broader original purpose of the Equal Protection Clause, which constitutionalized the core concept of personal equality as described in the Declaration of Independence. Thus, the apparent tension between active efforts to promote the progress of racial minority groups and the promise of personal equality for each individual, regardless of race, has been resolved in favor of the latter.

Nonetheless, the Supreme Court has upheld some forms of race-based affirmative action despite the application of strict scrutiny. Thus, the Court has said that racially conscious acts by legislatures, courts, or other state actors will meet strict scrutiny if the racially conscious act rectifies, in a narrowly tailored fashion, a previous governmental violation of equal protection, or— more controversially—if it furthers the compelling interest of racial diversity in a student body in higher education by including race as a positive element in an applicant’s profile. Grutter v. Bollinger (2003), Gratz v. Bollinger (2003). In 2007, however, the Court struck down two secondary school integration programs, voluntarily implemented by school districts, that assigned students to schools partially on the basis of race. Parents Involved in Community Schools v. Seattle Sch. Dist. (2007). In 2013, the Court refined its holding in Grutter, holding that although a court may show deference to a university’s assertion that the purpose of its diversity admissions program was “essential to its educational mission,” a court may not accord such deference to the means the university chose to implement its program. Rather, strict scrutiny requires that the university demonstrate “that each applicant is evaluated as an individual and not in a way that makes an applicant’s race or ethnicity the defining feature of his or her application.” Further, “the reviewing court must ultimately be satisfied that no workable race-neutral alternative would provide the educational benefits of diversity.” Fisher v. University of Texas at Austin (2013).

The Equal Protection Clause textually limits only state governments, hence it is literally inapplicable to the federal government. However, the Court has developed the doctrine that the Due Process Clause of the Fifth Amendment has an “equal protection component” with requirements equivalent to those of the Equal Protection Clause of the Fourteenth Amendment. See, e.g., Bolling v. Sharpe (1954). Equal protection doctrine (if not literally the Equal Protection Clause) has thus become applicable to all governmental action, whether state, local, or federal. Justice Sandra Day O’Connor summarized the Court’s current view in Adarand Constructors v. Pena (1995). First, she said, there is skepticism: “[A]ny official action that treats a person differently on account of his race or ethnic origin is inherently suspect.” Second, there is consistency: “the standard of review under the Equal Protection Clause is not dependent on the race of those burdened or benefited. . . .” Third, there is congruence: equal protection standards and analysis is the same as applied to both states and the federal government.