American courts review the constitutionality of laws using three levels of judicial scrutiny: rational basis review, intermediate scrutiny, and strict scrutiny. Each tier demands a different level of justification from the government. The more a law burdens a protected group or a fundamental right, the harder the government has to work to defend it. Rational basis is the most forgiving. Strict scrutiny is the most demanding, and laws rarely survive it.
Which tier a court picks usually decides the case. That is why so much constitutional litigation is really a fight over the standard of review rather than the merits of the law itself.
Rational Basis Review
Most laws face only rational basis review. A challenged law survives as long as it bears a rational relationship to some legitimate government interest. This covers the vast majority of economic and social welfare regulations: licensing requirements, zoning rules, tax structures, and age-based restrictions all fall here. Wealth classifications and regulations affecting people with disabilities also receive this level of review.1Justia. City of Cleburne v. Cleburne Living Center, Inc., 473 U.S. 432 (1985)
The person challenging the law carries the entire burden. They must show that no conceivable rational basis supports it. The government does not need to produce evidence that the law actually works, and it does not need to show that legislators considered the justification now being offered. In FCC v. Beach Communications (1993), the Court made this explicit: a “legislative choice is not subject to courtroom fact-finding and may be based on rational speculation unsupported by evidence or empirical data.”2Legal Information Institute. FCC v. Beach Communications, 508 U.S. 307 (1993) Courts can even hypothesize justifications the legislature never actually considered. If any plausible reason exists, the law stands.
This deference is a deliberate choice to stay out of economic policymaking. As the Court put it in Williamson v. Lee Optical (1955), “the day is gone when this Court uses the Due Process Clause of the Fourteenth Amendment to strike down state laws, regulatory of business and industrial conditions, because they may be unwise, improvident, or out of harmony with a particular school of thought.”3Justia. Williamson v. Lee Optical, Inc., 348 U.S. 483 (1955) The remedy for bad economic policy is the ballot box, not the courtroom. Laws reviewed under this standard almost always survive.
Rational Basis With Bite
Occasionally the Court nominally applies rational basis review but does so with noticeably less deference. Scholars call this “rational basis with bite.” It appears when a law looks like it exists to target a politically unpopular group rather than to serve any genuine policy goal.
In USDA v. Moreno (1973), the Court struck down a food stamp provision designed to exclude hippie communes, holding that “a bare congressional desire to harm a politically unpopular group cannot constitute a legitimate governmental interest.”4Library of Congress. U.S. Department of Agriculture v. Moreno, 413 U.S. 528 (1973) In City of Cleburne v. Cleburne Living Center (1985), the Court refused to create a new suspect classification for people with intellectual disabilities but still struck down a zoning ordinance that required a special permit for a group home, finding “no rational basis” for treating the home differently from boarding houses and hospitals already allowed in the area.1Justia. City of Cleburne v. Cleburne Living Center, Inc., 473 U.S. 432 (1985) And in Romer v. Evans (1996), the Court invalidated a Colorado constitutional amendment that stripped antidiscrimination protections from gay and lesbian residents, concluding that its “sheer breadth” was “so far removed from the reasons offered for it” that it raised “the inevitable inference that it is born of animosity toward the class that it affects.”5Justia. Romer v. Evans, 517 U.S. 620 (1996)
This is not an officially recognized fourth tier. But when a court senses that a law exists to punish a disfavored group rather than to serve a public purpose, deference evaporates fast, even without formally raising the scrutiny level.
Intermediate Scrutiny
Intermediate scrutiny applies to laws that classify people based on sex or legitimacy (whether someone’s parents were married). The government must show that the classification serves an important governmental objective and that the means chosen are substantially related to achieving it.6Legal Information Institute. Clark v. Jeter, 486 U.S. 456 (1988) The government carries the burden, and it cannot rely on stereotypes, overbroad generalizations, or justifications invented after the fact.
The standard came from Craig v. Boren (1976), which struck down an Oklahoma law allowing women to buy low-alcohol beer at 18 while making men wait until 21. The Court held that “classifications by gender must serve important governmental objectives and must be substantially related to achievement of those objectives.”7Legal Information Institute. Craig v. Boren, 429 U.S. 190 (1976) Oklahoma’s drunk-driving statistics did not clear that bar.
Two decades later, United States v. Virginia (1996) tightened the standard when the Court ordered the Virginia Military Institute to admit women. The justification for a sex-based classification “must be genuine, not hypothesized or invented post hoc in response to litigation,” and the government must offer an “exceedingly persuasive justification” for the distinction.8Legal Information Institute. United States v. Virginia, 518 U.S. 515 (1996) Broad generalizations about the preferences or abilities of men and women will not do.
The same tier protects children born to unmarried parents. Inheritance rules, benefit programs, and similar laws cannot treat these children differently without a substantial connection to an important government goal.6Legal Information Institute. Clark v. Jeter, 486 U.S. 456 (1988)
Commercial Speech
Intermediate scrutiny also governs regulations of commercial speech, meaning advertising and other speech that proposes a commercial transaction. The Court set out a four-part framework in Central Hudson Gas v. Public Service Commission (1980). The speech must concern lawful activity and not be misleading. The government interest in regulating it must be substantial. The regulation must directly advance that interest. And the regulation must not be more extensive than necessary to serve it.9Justia. Central Hudson Gas and Electric v. Public Service Commission, 447 U.S. 557 (1980)
Misleading or illegal commercial speech gets no protection; the government can ban it outright. Truthful advertising for legal products and services can be restricted only if the government proves a substantial interest, a direct connection between the restriction and that interest, and a reasonably narrow fit.
Strict Scrutiny
Strict scrutiny is the most demanding standard and functions almost as a presumption of unconstitutionality. It applies in two situations: when a law classifies people based on a suspect characteristic such as race, national origin, religion, or alienage, and when a law burdens a fundamental right.
The roots run back to Korematsu v. United States (1944), where the Court declared that “all legal restrictions which curtail the civil rights of a single racial group are immediately suspect” and that “courts must subject them to the most rigid scrutiny.”10Justia. Korematsu v. United States, 323 U.S. 214 (1944) The framework survived even as the decision upholding the Japanese internment order was effectively repudiated.
To clear strict scrutiny, the government must prove that the law is narrowly tailored to serve a compelling governmental interest.11Legal Information Institute. Grutter v. Bollinger, 539 U.S. 306 (2003) “Compelling” means more than important; it requires an interest of the highest order, such as remedying documented past discrimination or preserving national security. “Narrowly tailored” means the law cannot sweep more broadly than necessary. If a less restrictive approach would achieve the same goal, the broader law fails.
Suspect Classifications
Race is the paradigmatic suspect classification. In Adarand Constructors v. Peña (1995), the Court made clear that strict scrutiny applies to all racial classifications “whether imposed by a federal, state, or local actor,” including programs designed to benefit minority groups.12Justia. Adarand Constructors, Inc. v. Pena, 515 U.S. 200 (1995) Good intentions do not lower the standard. A race-based affirmative action program faces the same level of review as an overtly discriminatory law.
National origin and religion trigger the same analysis. Any law that distributes benefits or burdens along these lines must clear the compelling-interest and narrow-tailoring hurdles. Because those hurdles are so high, most laws subjected to strict scrutiny are struck down. That is where the familiar line about strict scrutiny being “strict in theory, fatal in fact” comes from.
Fundamental Rights
Strict scrutiny also kicks in when the government burdens a fundamental right. The recognized list includes the right to vote, freedom of speech, freedom of religion, the right to interstate travel, the right to marry, and the right to privacy, which covers decisions about contraception and family relationships. Some of these are spelled out in the Constitution’s text; others, like marriage and privacy, were recognized by the Court as implicit in the concept of ordered liberty.
Content-Based Speech Restrictions
Free speech doctrine shows strict scrutiny at work. In Reed v. Town of Gilbert (2015), the Court held that “content-based laws — those that target speech based on its communicative content — are presumptively unconstitutional and may be justified only if the government proves that they are narrowly tailored to serve compelling state interests.”13Justia. Reed v. Town of Gilbert, 576 U.S. 155 (2015) A law is content-based if it applies differently depending on the topic discussed or the message expressed. Once a court identifies a restriction as content-based on its face, strict scrutiny applies automatically. The court does not need to investigate the government’s actual motives.
Content-neutral restrictions receive intermediate scrutiny instead. The distinction matters a lot in practice. A ban on signs criticizing the government is content-based and faces near-certain invalidation. A general noise ordinance that applies equally regardless of message is content-neutral and much easier to defend.
How Courts Decide Which Tier Applies
Not every law that produces unequal outcomes triggers heightened scrutiny. The Court drew that line sharply in Washington v. Davis (1976), holding that a law is not unconstitutional under the Equal Protection Clause “solely because it has a racially disproportionate impact.”14Justia. Washington v. Davis, 426 U.S. 229 (1976) Disproportionate impact is relevant evidence, but standing alone it is not enough. The challenger must prove the government acted with a discriminatory purpose.
The Court laid out a roadmap for identifying that purpose in Village of Arlington Heights v. Metropolitan Housing Development Corp. (1977). Factors include the historical background of the decision, the specific sequence of events leading up to it, departures from normal procedures, and the legislative history, including statements by lawmakers and meeting minutes.15Legal Information Institute. Village of Arlington Heights v. Metropolitan Housing Development Corp., 429 U.S. 252 (1977) No single factor decides the question; courts conduct a holistic assessment.
This impact-versus-intent line has real consequences. A hiring test that disproportionately screens out applicants of a particular race does not violate the Equal Protection Clause unless the challenger can show the test was adopted or maintained because of its discriminatory effect rather than merely despite it. Federal civil rights statutes like Title VII separately prohibit unjustified disparate impact in employment, but that is a statutory standard, not a constitutional one.
Why the Tier Usually Decides the Case
The level of scrutiny a court selects often settles the outcome before the analysis really begins. Under rational basis review, the government barely has to show up; the challenger must disprove every conceivable justification, and courts will invent hypothetical reasons the legislature might have had.2Legal Information Institute. FCC v. Beach Communications, 508 U.S. 307 (1993) Under strict scrutiny, the government must prove its case with specificity, and anything less than the tightest possible fit between the law and its stated purpose leads to invalidation. Intermediate scrutiny falls predictably in between, demanding real justification but not perfection.
That is why so much constitutional litigation focuses on which tier applies rather than on the merits of the law itself. Getting a classification recognized as suspect or quasi-suspect, or framing a right as fundamental, is often the whole ballgame. A law regulating commercial advertising lives or dies under a different standard than a law restricting political speech, even though both involve the First Amendment. A policy that draws lines based on income gets near-automatic deference; the same policy drawing lines based on race faces near-automatic invalidation.