Carolene Products Footnote 4: Strict, Intermediate, Rational Basis

Footnote 4 of United States v. Carolene Products Co. is a 155-word passage in the Supreme Court’s 1938 opinion, written by Justice Harlan Fiske Stone, that proposed courts should apply tougher scrutiny to laws threatening individual liberties, restricting the political process, or targeting vulnerable minority groups.¹ It had nothing to do with the actual dispute in the case, only four justices joined the section that contained it, and yet it became the blueprint for how courts evaluate nearly every constitutional rights challenge today.

The Case It Was Buried In

The dispute itself was forgettable. Congress had passed the Filled Milk Act in 1923, making it a crime to ship skimmed milk blended with vegetable oil across state lines, and the Carolene Products Company was indicted for doing exactly that. The Court upheld the statute.¹

The timing is what mattered. The case arrived during the New Deal, when the Court was abandoning decades of aggressive interference with economic legislation. Throughout the early 1900s, judges had routinely struck down wage laws, labor protections, and similar regulations by second-guessing legislative judgments about economic policy. By 1938, that approach was collapsing. Stone used the opinion to announce that economic regulations would no longer face tough judicial review; courts would presume these laws constitutional and leave economic policy to elected officials.¹

That was the holding. The revolution was in the footnote.

What Footnote 4 Actually Says

Stone organized the footnote into three short paragraphs, each identifying a situation where the normal presumption of constitutionality might not apply. His language was deliberately tentative: each paragraph was phrased as a question the Court didn’t need to answer in this case, not as a definitive rule. That tentativeness is why the footnote is technically dicta. Each paragraph still planted a seed that grew into a distinct area of constitutional law.

The first paragraph suggested that courts should look more closely at laws that appear to violate specific protections in the Bill of Rights, including rights incorporated against state governments through the Fourteenth Amendment.² If a law restricts speech, prohibits religious exercise, or runs into another explicit constitutional guarantee, the usual deference to the legislature shrinks.

The second paragraph turned to democracy itself. Stone cited cases involving restrictions on voting, limits on political organizations, and government control over the flow of information. His logic was self-reinforcing. Deferential review assumes voters can fix bad laws through the political process; if the law itself blocks that process, the assumption collapses, and courts must step in because the normal self-correcting mechanism cannot function.²

The third paragraph was the most forward-looking. Stone asked whether “prejudice against discrete and insular minorities” might require “a correspondingly more searching judicial inquiry.”² The reasoning paralleled the second paragraph: if a group faces such entrenched bias that it cannot protect itself through normal politics, courts must provide the protection the ballot box will not. Stone specifically referenced statutes targeting religious, national, and racial minorities.

The Default Rule for Everything Else

The main body of the opinion established what lawyers now call rational basis review. When someone challenges an ordinary law as unconstitutional, courts start by assuming the legislature knew what it was doing. The challenger carries the entire burden of proving that the law has no rational connection to any legitimate government purpose.¹

The bar is extraordinarily low. A court applying rational basis review does not need the government to come forward with evidence justifying the law. The judge can supply a hypothetical justification on the government’s behalf. As long as anyone can imagine a plausible reason the legislature might have had for passing the law, it survives. In practice, rational basis review is almost impossible to fail. It applies to the vast majority of legislation, from tax codes to zoning rules to licensing requirements, and it reflects a basic principle: judges should not substitute their policy preferences for those of elected representatives.

Strict Scrutiny Grew From Paragraphs One and Three

The first and third paragraphs of Footnote 4 eventually gave rise to strict scrutiny, the most demanding test a court applies. The presumption flips. Instead of assuming the law is valid and forcing the challenger to disprove it, the court presumes the law is unconstitutional and forces the government to justify it. The government must demonstrate that the law serves a compelling interest and that it is narrowly tailored to achieve that interest using the least restrictive means available.¹

Strict scrutiny applies in two main situations. The first involves suspect classifications: when the government sorts people by race, national origin, or similar characteristics, courts treat the classification as inherently suspicious.³ The second involves fundamental rights. Some appear in the Constitution’s text, like free speech and religious exercise. Others the Court has recognized over time as implicit in constitutional liberty: the right to marry, the right to interstate travel, the right to privacy, the right to have children, and the right to custody of one’s children all qualify. Laws that burden any of these face strict scrutiny regardless of the group they affect.

Few laws survive this test. The government’s justification must be real, not invented after the fact to defend a lawsuit, and the law must be the least intrusive way to accomplish its goal. Strict scrutiny is sometimes called “strict in theory, fatal in fact” because the standard is so demanding that it almost always results in the law being struck down.

Intermediate Scrutiny Filled the Gap

Footnote 4 sketched a two-level system: deferential review for economic laws and heightened review for everything else. Over time, the Court recognized that some classifications deserved more attention than rational basis review but not the full weight of strict scrutiny. Gender-based classifications became the primary example.

In Craig v. Boren (1977), the Court formally established intermediate scrutiny. An Oklahoma law let women buy low-alcohol beer at 18 but required men to wait until 21. The Court struck it down and announced the test: a gender-based law must serve important governmental objectives and must be substantially related to achieving those objectives.⁴ The words matter. “Important” is a lower bar than “compelling,” and “substantially related” gives the government more room than “narrowly tailored.” Both requirements are still considerably harder to satisfy than rational basis review’s anything-goes standard.

The Court raised the bar further in United States v. Virginia (1996), which struck down the Virginia Military Institute’s male-only admissions policy. The Court held that the government must provide an “exceedingly persuasive justification” for any gender-based classification. That justification cannot rest on broad generalizations about differences between men and women, and it cannot be a post-hoc rationalization invented for litigation.⁵

Rational Basis With Bite

The three-tier framework does not capture everything courts actually do. In a handful of cases, the Supreme Court has applied rational basis review with noticeably more teeth than usual. Scholars call this “rational basis with bite,” and it tends to surface when the Court suspects a law was motivated by prejudice or hostility toward a particular group rather than any legitimate policy goal.

The leading example is City of Cleburne v. Cleburne Living Center (1985). A Texas city required a special zoning permit for a group home for people with intellectual disabilities but not for hospitals, nursing homes, or apartment buildings in the same area. The Court declined to classify intellectual disability as a suspect or quasi-suspect classification, so it nominally applied rational basis review. The review was anything but deferential. The Court examined each justification the city offered and rejected them all, concluding that the permit requirement “appears to rest on an irrational prejudice against the mentally retarded.” The Court held that “mere negative attitudes, or fear, unsubstantiated by factors which are properly cognizable in a zoning proceeding, are not permissible bases” for differential treatment.⁶

The same approach has surfaced in other contexts where the Court detected government animus toward a disfavored group. “Rational basis with bite” is academic shorthand, not an official legal term, and the Court has never formally acknowledged it as a distinct tier. The pattern is real: when a law seems driven by hostility rather than policy, courts applying rational basis review will actually scrutinize the government’s reasoning instead of rubber-stamping it.

Why a Footnote Carries This Much Weight

Footnote 4’s influence is wildly disproportionate to its authority at the time it was written. Only four justices joined the section containing it: Stone, Chief Justice Hughes, Justice Brandeis, and Justice Roberts. Justice Black explicitly declined to join that section. Justices Cardozo and Reed did not participate. Justice McReynolds dissented.¹ Four of seven participating justices is a majority, but a thin one, and the footnote itself was dicta: the Court did not need to address heightened scrutiny to uphold the Filled Milk Act.

None of that slowed its adoption. Over the following decades, the framework Stone sketched in three tentative paragraphs became the organizing principle of constitutional rights litigation. Courts used it to build the strict scrutiny test that dismantled racial segregation. They used it to develop intermediate scrutiny for gender discrimination. They used it to protect voting rights, free speech, and religious liberty from legislative overreach. The footnote endures because it answered a question the Court could no longer avoid after abandoning aggressive economic review: if judges would stop policing business regulations, what would they police instead? Stone’s answer, compressed into a footnote because he couldn’t get enough colleagues to put it in the main text, turned out to be the most durable framework the Court has ever produced.

1
Justia U.S. Supreme Court Center. United States v. Carolene Products Co., 304 U.S. 144 (1938)
2
Legal Information Institute. United States v. Carolene Products Co.
3
Constitution Annotated. Facially Neutral Laws Implicating Suspect Classifications
4
Justia U.S. Supreme Court Center. Craig v. Boren, 429 U.S. 190 (1976)
5
Justia U.S. Supreme Court Center. United States v. Virginia, 518 U.S. 515 (1996)
6
Justia U.S. Supreme Court Center. City of Cleburne v. Cleburne Living Center, Inc., 473 U.S. 432 (1985)