Skip to main content

Equal Protection of the Laws

Last Updated: 2018

One fundamental characteristic of the American constitutional system has been the precept that a law cannot discriminate among individuals who are essentially similar. Americans believe that laws must not distinguish between different groups. The legal challenge raised by equal protection jurisprudence has been to determine when such distinctions are appropriate and constitutional. The primary articulation of this understanding is found in the Fourteenth Amendment to the Constitution, passed in 1868 after the end of the Civil War. While this amendment was designed to ensure that newly freed slaves as well as “free blacks” were granted full citizenship, the Fourteenth Amendment also placed specific responsibilities on the states as to how they must treat their citizens. More specifically, the Fourteenth Amendment prohibits each state from making or enforcing any law “which shall abridge the privileges or immunities of citizens of the United States; . . . deprive any person of life, liberty, or property without due process of law; . . . [or] deny to any person within its jurisdiction the equal protection of the laws.” In Section 5 of the Fourteenth Amendment, Congress is empowered to enforce these guarantees through federal legislation. The history of equal protection in the United States has not been one where equality of all citizens has been uniformly valued; in fact, much of our political and legal debate has centered on the questions of what is meant by “equality” and how it best may be secured. One source of these debates is the inherent tension between personal liberty and societal equality—two values equally promised by the Constitution, but guaranteed to be in conflict. Justice Robert Jackson, in his concurrence in Railway Express Agency v. New York (1949), underscored the importance of equal protection for citizens and the special role the courts play in its enforcement:

The framers of the Constitution knew, and we should not forget today, that there is no more effective practical guaranty against arbitrary and unreasonable government than to require that the principles of law which officials would impose upon a minority must be imposed generally. Conversely, nothing opens the door to arbitrary action so effectively as to allow those officials to pick and choose only a few to whom they will apply legislation and thus to escape the political retribution that might be visited upon them if larger numbers were affected. Courts can take no better measure than to assure that laws will be just than to require that laws be equal in operation. (Railway Express Agency v. New York 336 U.S. 106)

By guaranteeing equal protection of the laws, the Fourteenth Amendment was designed to prevent states from treating people who were newly freed from slavery differently from other citizens. This amendment has had significance well beyond the eradication of slavery. Equal protection requires that individuals be similarly valued before the law and that personal characteristics such as race, gender, and religion can rarely enter into legislative determinations. However, statutes do not and cannot treat people identically; consequently, there are certain types of classifications that are considered constitutional under the Equal Protection Clause. For example, truck drivers are often given a lower speed limit because trucks are heavier and need longer stopping distances than cars. Since truck drivers (as opposed to car drivers) are not provided special protection by the Constitution, states can easily make this legal distinction. The Supreme Court and the lower federal courts create tests to determine when laws distinguishing between groups and classes of citizens are constitutional and when they are unconstitutional. One significant and continuing point of conflict has been the identification of characteristics that may be legally considered as having a “protected status” under the law. This status ensures that the courts will look more stringently at laws that treat such designated groups differently from the remainder of the population. Over time, race has been given greater protection while gender has received less protection. Age, poverty, sexual preference, and disability have been granted even fewer protections.


In 1869, the State of Louisiana decided to award a single company exclusive rights to slaughter animals for a twenty-five-year period. A lawsuit was filed by an association of New Orleans butchers. These men argued that their equal protection rights, among others, were violated by this state-created monopoly. The Supreme Court first interpreted the Equal Protection Clause in their 1873 decision of The Slaughterhouse Cases. The Court determined that the Equal Protection Clause was not designed for the protection of all citizens, limiting the application of the Fourteenth Amendment to primarily protect African Americans. As Justice Samuel Miller in his majority opinion noted, “The existence of laws in the states where the emancipated negroes resided, which discriminated with gross injustice and hardship against them as a class, was the evil to be remedied by this clause, and by it such laws are forbidden.” Furthermore, the Court applied this doctrine to African Americans in the 1880 case of Strauder v. West Virginia, in which a state law that excluded blacks from jury duty was found to be unconstitutional. Using the powers granted them under Section 5 of the Fourteenth Amendment, the Reconstruction Congress passed numerous laws designed to protect blacks from Ku Klux Klan violence, private and state discrimination, and other forms of harassment. However, the Court quickly indicated that the federal power to protect these new citizens was greatly limited. In the 1883 Civil Rights Cases, the Court deemed unconstitutional the Civil Rights Act of 1875, which “prohibited private persons from violating the rights of other persons to the full and equal enjoyment of public accommodations on the basis of race and color.” Through a series of legal renderings, the Court found that many of the federal laws passed by Congress to protect blacks in the South were too broad. The Fourteenth Amendment was not meant to prevent one citizen from harming another; the Court determined that this amendment only protected citizens from state action.

In 1896, the Court extended this reasoning and recognized that state laws distinguishing between races could be constitutional; this decision allowed Jim Crow segregation laws to continue both in the South and in the North. Plessy v. Ferguson (1896) determined that the Equal Protection Clause allows legally mandated separate facilities for black and white citizens, as long as these facilities were equal. By “equal,” the Court required that black citizens have access to the same type of facilities (e.g., public restrooms, drinking fountains, and public transportations) as whites, but did not require that such facilities had to be of the same quality. States were allowed to distinguish on the basis of race; equal protection was interpreted as requiring equal availability, not equal quality. This was deemed “separate but equal.”


Over time, the Supreme Court has developed several different standards to help determine the constitutionality of state laws under the Equal Protection Clause. Historically, the first standard has come to be known as “ordinary scrutiny.” Ordinary scrutiny was initially used for all forms of equal protection litigation. To meet this standard of ordinary scrutiny, the state must simply demonstrate that there is a rational foundation for the discriminatory law. This level of scrutiny is known as the “minimal rationality” standard. Under most circumstances, a state simply had to demonstrate that there was a rational foundation for the distinction between groups. For example, many states fund public school education based on property taxes. The result is that there may be great disparities between school districts in terms of assessed property values and consequently the funds spent per pupil. In San Antonio Independent School District v. Rodriguez (1973), a group of Mexican American parents challenged these disparities before the Supreme Court. The Supreme Court, using ordinary scrutiny, found that the state funding system was not based on a discriminatory purpose; instead, it was designed to assure “a basic education for every child in the state” and to permit and encourage “a large measure of participation in and control of each district’s school at the local level.” The statute therefore bore a rational relationship to a legitimate state purpose. If a state cannot demonstrate a relationship between the state objective and the discrimination required by the statute, then the state law is in violation of the Equal Protection Clause. This approach assumes that state legislation is constitutional, and the burden of proof falls heavily on the litigant challenging the validity of the statute.


It was not until the 1938 case of United States v. Carolene Products Company that the Court suggested there might be another way of interpreting the Equal Protection Clause, providing more protection to individuals. Footnote 4 of the majority decision suggested that the Court apply a higher degree of scrutiny to legislation that discriminated against minorities who were deemed “discrete and insular.” The Court did not initially define these terms; rather, the determination of which groups were provided this higher level of protection evolved through legislation and litigation. In Footnote 4, the Court was suggesting a “strict scrutiny” test, a means of providing greater protection to “suspect classifications”: groups that have immutable or unchangeable characteristics and a history of emotionally based antagonism toward them, which is otherwise known as “invidious discrimination.” Suspect classifications included groups of citizens who were separated from other citizens by virtue of being religious, ethnic, or racial minorities. If state legislation identifies such groups for differential treatment, federal courts assume the statute to be unconstitutional—unless the state can demonstrate that the classification is necessary to achieve a permissible state objective. The Court extended this highest standard, called “strict scrutiny,” to all laws that violate fundamental freedoms (such as religion, speech, and press), legislation that restricts political rights (such as the right to vote, politically organize, peaceably assemble, or disseminate information), and statutes impacting suspect classes. In Carolene Products, the Court introduced a dual approach to the Equal Protection Clause—a more deferential, ordinary scrutiny of legislation regulating economic rights, and a more meticulous, strict scrutiny of statutes limiting civil rights and liberties.

Strict scrutiny of the Equal Protection Clause was considered in the case of Korematsu v. United States (1944). In the majority decision, the Court upheld the 1942 Executive Order no. 34 authorizing the creation of “military zones,” in which the military could exclude individuals to prevent sabotage and espionage. Justified by claims of national security, tens of thousands of Japanese Americans on the West Coast were given curfews, evacuated, and interned in “relocation camps.” Because this law applied only to American citizens of Japanese ancestry, it was challenged as a violation of the Equal Protection Clause of the Fourteenth Amendment. In his majority opinion, Justice Hugo Black stated, It should be noted, to begin with, that all legal restrictions which curtail the civil rights of a single racial group are immediately suspect. That is not to say that all such restrictions are unconstitutional. It is to say that courts must subject them to the most rigid [strict] scrutiny. Pressing public necessity may sometimes justify the existence of such restrictions; racial antagonism never can. (Korematsu v. United States 324 U.S. 885)

While the Equal Protection Clause was cited in the case, it was not perceived by the Court to be applicable against presidential claims of national security. In later years, the national security claims have been reevaluated, and the Japanese exclusion cases are now perceived to be one of the greater violations of civil rights in U.S. history.

Brown v. Board of Education (1954) is famous because it provided a clear new definition of the Equal Protection Clause and overturned Plessy v. Ferguson; equal protection is now understood as meaning that laws mandating segregation are by definition unequal. Attempts to make segregated facilities equal in a qualitative sense could not save legally separated school systems, and by extension, other manifestations of Jim Crow (e.g., water fountains and public restrooms). In the process of deciding Brown, the Court also determined that the Equal Protection Clause applies to federal legislation. One of the five school desegregation cases that made up Brown was located in Washington, D.C.—Bolling v. Sharpe. Because Washington, D.C. is not a state, its citizens receive no protections under the Fourteenth Amendment. The Supreme Court ruled in Bolling (1955) that inherent within the Fifth Amendment’s due process provision is a federal guarantee of the equal protection of the laws. It was in the 1971 case of Graham v. Richardson that the Supreme Court also extended strict scrutiny to laws discriminating against aliens or non-U.S. citizens. In subsequent years, the Court has varied the standard of equal protection used in cases related to alienage and immigration. Most notably, the Court has overturned state laws limiting specific state jobs to citizens using ordinary scrutiny. Most recently, in Torres v. Lynch (2016) equal protection did not protect a lawful resident from being expelled from the United States after conviction for an aggravated felony.

An Emerging New Standard: Intermediate Scrutiny

Ordinary scrutiny has been the benchmark for most equal protection claims. However, the exception carved out by strict scrutiny has provided a new direction for courts considering statutes making racial distinctions. While gender fits many of the attributes inherent in suspect classification—an immutable characteristic and a history of “invidious” discrimination—in most circumstances, the Supreme Court has not considered gender as meeting the required criteria for strict scrutiny.

Historically, gender fell under ordinary scrutiny. In 1961, the U.S. Supreme Court in Hoyt v. Florida (1961) found that a Florida statute requiring women to register for jury service while men were automatically placed in jury pools was seen as not violating equal protection claims. The Court found a reasonable relationship between the statute and the belief that women are the “center of the home and family life” and thereby warrant different treatment under the law. This was the last case in which the Supreme Court used ordinary scrutiny to evaluate the constitutionality of laws relating to gender distinctions. It was not until Reed v. Reed (1971) that sex discrimination would be found unconstitutional under the Equal Protection Clause. After this decision, the Court crafted a new equal protection standard designed solely for gender: intermediate scrutiny. This stricter standard inquires if the challenged classification is “really reasonable”— does it serve an important governmental objective, and is it substantially related to those ends? Despite defining this new standard it was not until Craig v. Boren (1976) did the Supreme Court recognized its reliance on intermediate, or “semistrict,” scrutiny, in cases related to gender.


While women slowly gained protection from statutory discrimination under the Equal Protection Clause, racial minorities saw the clause’s meaning change from an articulation of group protections to a perception that the Fourteenth Amendment only prohibited discrimination against individuals. In the 1989 case of Richmond v. Croson and the 1995 Adarand Constructors, Inc. v. Pena case, the Supreme Court determined that any state legislation considering race would be considered under the requirements of strict scrutiny. Prior to these decisions, statutes designed to incorporate previously excluded groups (such as affirmative action legislation) were understood to be benign forms of discrimination and not included under the strict scrutiny parameters. The Rehnquist Court in these decisions determined that the Fourteenth Amendment required any form of racial consideration in a law, regardless of intent to include or exclude, to be constitutionally questionable. This does not mean that affirmative action plans are unconstitutional, but it does require that all such state legislation demonstrate that the law is as narrowly tailored as possible and necessary for the achievement of a legitimate state objective.

At the beginning of the twenty-first century, equal protection moved beyond the traditional considerations of race and gender. In the 2000 case of Bush v. Gore, most members of the Court found that the presidential ballot recounting procedures in Florida violated the Equal Protection Clause. The Court has not applied equal protection to subsequent voting claims. Other groups, including the LGBQTI and physically and cognitively impaired communities, have attempted to heighten the level of scrutiny used by courts in equal protection litigation to mixed success. In 2001, the U.S. Supreme Court in University of Alabama v. Garrett found Section 1 of the 1990 Americans with Disabilities Act to be unconstitutional because it provided a disabled individual the ability to challenge state discrimination in federal court. The Court determined that “disability” was not a suspect classification under the Fourteenth Amendment; consequently, states are permitted to pass legislation and take other actions that may disadvantage disabled people. According to Garrett, such action does not violate the Equal Protection Clause, as long as the state can articulate a rational justification for their action and meet the requirements of ordinary scrutiny.

Similar rulings have been made in the classifications of age and relative wealth. The Court has consistently determined that poverty is not an immutable characteristic; instead, it is subject to change over the course of an individual’s life. Consequently, laws that disadvantage the poor are evaluated under ordinary scrutiny, as the Rodriguez case revealed. Age is also not found to be a suspect classification, although age discrimination, like discrimination against people with disabilities, has been clearly prohibited by a number of federal laws. In 2000, the Court reinforced this ruling in Kimel v. Florida Board of Regents, noting that “[o]ld age . . . does not define a discrete and insular minority because all persons, if they live out normal life spans, will experience it.” While questions of who is covered under protected status remain vibrant before the Court, ordinary scrutiny has been consistently applied to most forms of discrimination outside of race, alienage, and gender.

The Court did find in 1996, in the case of Romer v. Evans, that a Colorado constitutional amendment banning the inclusion of homosexuals as a protected class was a violation of the Equal Protection Clause. Amendment 2 prevented any Colorado local government from protecting the rights of gays and lesbians through governmental activity. Justice Anthony Kennedy, in the majority opinion, noted that the law did not merely prevent a group from being granted special rights, but instead “imposes a special disability upon those persons alone. Homosexuals are forbidden the safeguards that others enjoy or may seek without constraint.” Kennedy found no need to apply strict scrutiny; in fact, he found that the law could not even pass the lowest level of scrutiny.

As states differed in their determination as to whether their own constitution’s equal protection clauses protected same-sex marriages as a civil right, this question came to the Supreme Court. In addressing sexual orientation, the Supreme Court had generally preferred to use the Due Process Clause to protect sexuality as a behavior, not as an identity. This changed in the 2015 decision of Obergefell v. Hodges when the Supreme Court found the Equal Protection Clause to guarantee the right of same-sex couples to marry. Justice Kennedy noted in his majority opinion,

… in interpreting the Equal Protection Clause, the Court has recognized that new insights and society understandings can reveal unjustified inequality within our most fundamental institutions that once passed unnoticed and unchallenged (576 U.S. ___).

The changing interpretation of the Equal Protection Clause has shaped and will continue to define legal standards in the United States. The reframing of protected classes and the increased coverage of individual rights, as well as the altered federal legal standards, have been mirrored or anticipated by the interpretations of the state equal protection clauses.

SEE ALSO: ”Brown v. Board of Education”Fourteenth Amendment”Plessy v. Ferguson””Reed v. Reed”Slaughterhouse Cases


Judith A. Baer, Equality under the Constitution: Reclaiming the Fourteenth Amendment (Ithaca, NY: Cornell University Press, 1983); Stanley H. Friedelbaum, “State Equal Protection: Its Diverse Guises and Effects,” Albany Law Review 66 (2003): 599; Pamela S. Karlan, “Equal Protection, Due Process, and the Stereoscopic Fourteenth Amendment,” McGeorge Law Review 33 (Spring 2002): 473; and Donald G. Nieman,Promises to Keep: African-Americans and the Constitutional Order, 1776 to the Present (New York: Oxford University Press, 1991).