Landmark Supreme Court Decisions
The Supreme Court of the United States has decided thousands of cases since its first session in 1790, but a relatively small number of decisions have fundamentally shaped the constitutional order, redefined the relationship between government and individual rights, and altered the trajectory of American society. These landmark decisions established judicial review, ended legal segregation, defined the scope of criminal defendants' rights, expanded the reach of the Commerce Clause, and determined the boundaries of constitutional protections for speech, privacy, and equality. This page surveys twenty of the most consequential decisions in the Court's history, organized chronologically, explaining the facts, holdings, reasoning, and enduring significance of each.
Marbury v. Madison, 5 U.S. 137 (1803)
Issue: Whether the Supreme Court has the power to declare acts of Congress unconstitutional.
William Marbury sought a writ of mandamus from the Supreme Court to compel Secretary of State James Madison to deliver his judicial commission, which had been signed by outgoing President John Adams but not delivered before the change of administration. Chief Justice John Marshall's opinion held that Marbury was entitled to his commission but that the Court could not issue the writ because Section 13 of the Judiciary Act of 1789, which purported to grant the Court original jurisdiction to issue writs of mandamus, was unconstitutional — it expanded the Court's original jurisdiction beyond what Article III permitted.
Significance: Marbury established the foundational principle of judicial review — the power of the federal courts to invalidate laws that conflict with the Constitution. Marshall's assertion that "it is emphatically the province and duty of the judicial department to say what the law is" remains the single most important sentence in American constitutional law.
McCulloch v. Maryland, 17 U.S. 316 (1819)
Issue: Whether Congress has the power to establish a national bank, and whether a state may tax it.
Maryland imposed a tax on the Bank of the United States, and the bank's cashier, James McCulloch, refused to pay. Chief Justice Marshall upheld Congress's power to charter the bank under the Necessary and Proper Clause, holding that "necessary" means useful or conducive — not indispensable — to the exercise of an enumerated power. Marshall also held that Maryland could not tax the bank because "the power to tax involves the power to destroy," and a state cannot destroy an instrument of the federal government.
Significance: McCulloch established the doctrine of implied powers and the broad construction of the Necessary and Proper Clause that has enabled the vast expansion of federal legislative authority. The decision also reinforced federal supremacy over the states.
Gibbons v. Ogden, 22 U.S. 1 (1824)
Issue: The scope of Congress's power to regulate interstate commerce.
New York had granted a monopoly on steamboat navigation in its waters. Aaron Ogden, who held a license under the monopoly, sued Thomas Gibbons, who operated steamboats under a federal coasting license. Marshall held that Congress's power to regulate "commerce among the several states" is plenary, extends to all commercial intercourse that affects more than one state, and supersedes conflicting state law.
Significance: Gibbons established the expansive interpretation of the Commerce Clause that would eventually become the constitutional basis for the modern federal regulatory state.
Dred Scott v. Sandford, 60 U.S. 393 (1857)
Issue: Whether a person of African descent could be a citizen of the United States and whether Congress could prohibit slavery in federal territories.
Dred Scott, an enslaved man who had been taken to free territories, sued for his freedom. Chief Justice Roger Taney held that persons of African descent, whether enslaved or free, were not citizens of the United States and had "no rights which the white man was bound to respect." The Court also held that the Missouri Compromise, which prohibited slavery in certain federal territories, was unconstitutional because it deprived slaveholders of their property without due process of law.
Significance: Dred Scott is universally regarded as the worst decision in Supreme Court history. It inflamed sectional tensions that led to the Civil War and was effectively overruled by the Thirteenth Amendment (abolishing slavery) and the Fourteenth Amendment (granting citizenship to all persons born in the United States).
Plessy v. Ferguson, 163 U.S. 537 (1896)
Issue: Whether a state law requiring racial segregation on railroads violated the Equal Protection Clause.
Homer Plessy, a man of mixed race, was arrested for sitting in a whites-only railroad car in Louisiana. The Court upheld the segregation law, holding that "separate but equal" facilities satisfied the Fourteenth Amendment's equal protection guarantee. Justice John Marshall Harlan dissented, declaring that "our Constitution is color-blind."
Significance: Plessy provided the constitutional framework for Jim Crow segregation for nearly six decades, legitimating a system of racial apartheid that pervaded every aspect of Southern public life until it was overturned by Brown v. Board of Education.
Brown v. Board of Education, 347 U.S. 483 (1954)
Issue: Whether racially segregated public schools violate the Equal Protection Clause.
The case consolidated challenges to school segregation from Kansas, South Carolina, Virginia, and Delaware. Chief Justice Earl Warren's unanimous opinion held that "separate educational facilities are inherently unequal" and that racial segregation in public schools violates the Fourteenth Amendment. The decision explicitly overruled Plessy v. Ferguson's application to public education.
Significance: Brown is the most important civil rights decision in Supreme Court history. It dismantled the legal foundation of Jim Crow, catalyzed the civil rights movement, and established the principle that government-mandated racial segregation is per se unconstitutional.
Mapp v. Ohio, 367 U.S. 643 (1961)
Issue: Whether the exclusionary rule — prohibiting the use of illegally obtained evidence — applies to state criminal proceedings.
Police conducted a warrantless search of Dollree Mapp's home and found obscene materials. The Court held that the Fourth Amendment's protection against unreasonable searches and seizures, and the exclusionary rule as a remedy for violations, applies to the states through the Fourteenth Amendment's Due Process Clause.
Significance: Mapp extended the exclusionary rule to state courts, establishing a uniform national standard for the admissibility of evidence obtained through unconstitutional police conduct.
Gideon v. Wainwright, 372 U.S. 335 (1963)
Issue: Whether the Sixth Amendment right to counsel requires states to provide attorneys to criminal defendants who cannot afford them.
Clarence Earl Gideon was charged with felony breaking and entering in Florida. Too poor to afford a lawyer, he requested that the court appoint one. The court refused, as Florida law provided appointed counsel only in capital cases. Gideon was convicted. The Supreme Court unanimously reversed, holding that the Sixth Amendment's right to counsel is fundamental and obligatory upon the states through the Fourteenth Amendment.
Significance: Gideon established the constitutional right to appointed counsel for indigent defendants in all felony cases, leading to the creation of public defender systems across the country.
New York Times Co. v. Sullivan, 376 U.S. 254 (1964)
Issue: Whether a state defamation action by a public official against a newspaper violates the First Amendment.
L.B. Sullivan, a Montgomery, Alabama, city commissioner, sued the New York Times over an advertisement that contained minor factual inaccuracies about police conduct during civil rights protests. The Court held that the First Amendment requires public officials suing for defamation to prove "actual malice" — that the defendant published the statement with knowledge of its falsity or with reckless disregard for the truth.
Significance: Sullivan revolutionized American defamation law, establishing strong First Amendment protections for criticism of public officials and ensuring that debate on public issues remains "uninhibited, robust, and wide-open."
Griswold v. Connecticut, 381 U.S. 479 (1965)
Issue: Whether a state law prohibiting the use of contraceptives violates the Constitution.
Connecticut law made it a crime to use contraceptives or to assist anyone in their use. The Court struck down the law, holding that the Constitution protects a right to privacy that, while not explicitly mentioned in the text, emanates from the "penumbras" and "emanations" of the First, Third, Fourth, Fifth, and Ninth Amendments.
Significance: Griswold established the constitutional right to privacy, which became the doctrinal foundation for subsequent decisions protecting reproductive autonomy, sexual privacy, and personal decision-making.
Miranda v. Arizona, 384 U.S. 436 (1966)
Issue: Whether the Fifth Amendment privilege against self-incrimination requires law enforcement to inform suspects of their rights before custodial interrogation.
Ernesto Miranda was arrested and confessed to kidnapping and rape after two hours of police interrogation without being informed of his right to remain silent or his right to an attorney. The Court held that the prosecution may not use statements from custodial interrogation unless it demonstrates that the defendant was informed of the right to remain silent, that any statement may be used against them, and that they have the right to an attorney.
Significance: The "Miranda warnings" are among the most widely recognized legal protections in American law. The decision established clear procedural safeguards for custodial interrogation that apply in every jurisdiction in the country.
Loving v. Virginia, 388 U.S. 1 (1967)
Issue: Whether a state law prohibiting interracial marriage violates the Constitution.
Richard Loving (white) and Mildred Jeter (Black and Native American) were convicted under Virginia's Racial Integrity Act for marrying in the District of Columbia and returning to Virginia. The Court unanimously struck down the law, holding that marriage is a fundamental right and that restricting it based on race violates both the Equal Protection Clause and the Due Process Clause.
Significance: Loving invalidated anti-miscegenation laws in 16 states and established that marriage is a fundamental constitutional right subject to strict scrutiny when burdened by government action.
Roe v. Wade, 410 U.S. 113 (1973)
Issue: Whether the Constitution protects a right to terminate a pregnancy.
Jane Roe (a pseudonym for Norma McCorvey) challenged a Texas law criminalizing abortion except to save the life of the mother. The Court held that the right to privacy encompasses a woman's decision to terminate a pregnancy, but that this right must be balanced against the state's interests in protecting prenatal life and maternal health. The Court established a trimester framework governing the permissible scope of state regulation.
Significance: Roe was one of the most consequential and controversial decisions in Supreme Court history, establishing a constitutional right to abortion that persisted for nearly 50 years. It was overruled by Dobbs v. Jackson Women's Health Organization, 597 U.S. 215 (2022), which held that the Constitution does not confer a right to abortion and returned the regulation of abortion to the states.
United States v. Nixon, 418 U.S. 683 (1974)
Issue: Whether the President possesses an absolute privilege to withhold evidence from a criminal proceeding.
A federal grand jury subpoenaed tape recordings of President Nixon's conversations as part of the Watergate investigation. Nixon asserted executive privilege and refused to comply. The Court unanimously held that while a qualified executive privilege exists to protect confidential presidential communications, it does not extend to withholding evidence needed in a criminal prosecution. The President must comply with the subpoena.
Significance: Nixon established that the President is not above the law and that executive privilege, while real, has limits. Nixon resigned the presidency two weeks after the decision.
Regents of the University of California v. Bakke, 438 U.S. 265 (1978)
Issue: Whether a university's use of racial quotas in admissions violates the Equal Protection Clause.
Allan Bakke, a white applicant, was denied admission to the UC Davis medical school, which reserved 16 of 100 seats for minority applicants. Justice Lewis Powell's controlling opinion held that rigid racial quotas violate the Equal Protection Clause but that race may be considered as one factor among many in a holistic admissions process designed to achieve student body diversity.
Significance: Bakke established the framework for affirmative action in higher education that persisted for over four decades, until the Court effectively ended race-conscious admissions in Students for Fair Admissions v. Harvard, 600 U.S. 181 (2023).
Texas v. Johnson, 491 U.S. 397 (1989)
Issue: Whether burning the American flag as a form of political protest is protected by the First Amendment.
Gregory Lee Johnson burned a flag outside the 1984 Republican National Convention in Dallas to protest the policies of the Reagan administration. The Court held, 5-4, that flag burning is expressive conduct protected by the First Amendment. Justice William Brennan's majority opinion stated that "if there is a bedrock principle underlying the First Amendment, it is that the government may not prohibit the expression of an idea simply because society finds the idea itself disagreeable or offensive."
Significance: Johnson affirmed that the First Amendment protects even deeply offensive forms of political expression, establishing a principle that the government cannot punish symbolic speech based on its content or viewpoint.
Citizens United v. Federal Election Commission, 558 U.S. 310 (2010)
Issue: Whether the government may prohibit corporations and unions from spending money on independent political expenditures.
Citizens United, a nonprofit corporation, sought to distribute a documentary film critical of Hillary Clinton within 30 days of a primary election, in violation of the Bipartisan Campaign Reform Act's restrictions on corporate-funded electioneering communications. The Court held, 5-4, that the First Amendment prohibits the government from restricting independent political expenditures by corporations, associations, and labor unions.
Significance: Citizens United transformed the landscape of American campaign finance by removing limits on independent corporate and union political spending, leading directly to the creation of Super PACs and a dramatic increase in outside spending in federal elections.
Obergefell v. Hodges, 576 U.S. 644 (2015)
Issue: Whether the Constitution requires states to license and recognize same-sex marriages.
Jim Obergefell and other plaintiffs challenged state laws in Ohio, Michigan, Kentucky, and Tennessee that defined marriage as between a man and a woman. Justice Anthony Kennedy's majority opinion held that the fundamental right to marry is guaranteed to same-sex couples by the Due Process Clause and the Equal Protection Clause of the Fourteenth Amendment. Kennedy identified four principles supporting this conclusion: individual autonomy in intimate choices, the unique importance of the marriage bond to two people, the protection of children and families, and marriage's role as a keystone of social order.
Significance: Obergefell established marriage equality nationwide, requiring all states to issue marriage licenses to same-sex couples and to recognize same-sex marriages performed in other states.
Dobbs v. Jackson Women's Health Organization, 597 U.S. 215 (2022)
Issue: Whether the Constitution confers a right to abortion.
Mississippi enacted a law banning most abortions after 15 weeks of pregnancy, directly challenging the viability framework established in Roe v. Wade and reaffirmed in Planned Parenthood v. Casey, 505 U.S. 833 (1992). Justice Samuel Alito's majority opinion held that the Constitution does not confer a right to abortion, that Roe and Casey were egregiously wrong, and that the authority to regulate abortion is returned to the people and their elected representatives in the states.
Significance: Dobbs overruled nearly 50 years of precedent and triggered an immediate and dramatic shift in abortion access across the country, with approximately half the states moving to restrict or ban abortion and the other half moving to protect or expand access.
National Federation of Independent Business v. Sebelius, 567 U.S. 519 (2012)
Issue: Whether the Affordable Care Act's individual mandate and Medicaid expansion exceed congressional power.
Chief Justice John Roberts' opinion held that Congress could not compel individuals to purchase health insurance under the Commerce Clause, because the Commerce Clause authorizes regulation of existing commercial activity, not the compulsion of individuals to enter commerce. However, the Court upheld the mandate as a valid exercise of the Taxing Power, since the penalty for not purchasing insurance functioned as a tax. The Court also held that Congress could not threaten to withdraw all existing Medicaid funding from states that declined the ACA's Medicaid expansion, characterizing this condition as unconstitutionally coercive.
Significance: NFIB established outer limits on both the Commerce Clause and the Spending Clause, while preserving the ACA's core provisions. The Medicaid holding — the first time the Court found a condition on federal spending to be unconstitutionally coercive — has significant implications for the structure of cooperative federalism programs.
The Court's Evolving Role
The cases surveyed here span more than two centuries of constitutional adjudication and reflect the Supreme Court's extraordinary power to shape American law and society. The Court has been the institution that established judicial review, dismantled legal segregation, defined the rights of criminal defendants, expanded and contracted reproductive rights, redefined the scope of federal power, and determined the legal meaning of equality.
The Court's legitimacy rests on a paradox: nine unelected justices, serving life tenure, exercise the power to overrule the democratic decisions of Congress, state legislatures, and the American people. The justification for this power lies in the constitutional structure itself — the Constitution's status as supreme law requires an institution with the authority to enforce its commands against the other branches and the states. Whether the Court exercises that authority wisely, and whether its decisions reflect the Constitution's meaning or the justices' preferences, are questions that each generation of Americans must answer for itself.