The most important Supreme Court cases are the ones that changed how Americans live, vote, speak, marry, and interact with their government. The Court hears fewer than 80 cases a year out of roughly 7,000 petitions, and a small handful of those decisions have reshaped the country more than any statute Congress has passed. The rulings below are grouped by the constitutional question they answered, starting with the one that made all the others possible.
The Case That Made the Court
Every other decision on this list exists because of Marbury v. Madison. In 1803, Chief Justice John Marshall declared that the Constitution is the supreme law of the land and that any act of Congress conflicting with it is void. He also claimed for the judiciary the authority to make that call. “It is emphatically the province and duty of the Judicial Department to say what the law is,” Marshall wrote, and that sentence created the doctrine of judicial review.1Justia U.S. Supreme Court Center. Marbury v. Madison, 5 U.S. 137 (1803) Without it, the Court would have no mechanism to strike down unconstitutional laws, and the balance of power among the three branches would look nothing like what it does today.
Ending Segregation and Defining Equal Protection
The Fourteenth Amendment’s Equal Protection Clause has driven some of the Court’s most visible changes to American society. Three cases trace the arc from dismantling Jim Crow to the current debate over how race can be used in law.
Brown v. Board of Education
In 1954, the Court unanimously ruled that racial segregation in public schools violated the Equal Protection Clause. The opinion struck at the “separate but equal” doctrine that had allowed states to maintain racially divided institutions since 1896. The Court found that separating children by race “generates a feeling of inferiority as to their status in the community that may affect their hearts and minds in a way unlikely ever to be undone,” and concluded that separate educational facilities are inherently unequal.2Justia U.S. Supreme Court Center. Brown v. Board of Education of Topeka, 347 U.S. 483 (1954) The decision cracked the legal foundation of Jim Crow and set the stage for the civil rights movement that followed.
Loving v. Virginia
Richard Loving, a white man, and Mildred Jeter, a Black woman, married in Washington, D.C., then returned to Virginia, where their marriage was a felony. They pleaded guilty and were given a choice between one year in prison or leaving the state for 25 years. They left, then challenged the law.3Justia U.S. Supreme Court Center. Loving v. Virginia, 388 U.S. 1 (1967) In 1967, the Court struck it down unanimously, holding that marriage is a fundamental right and that restricting it based on race violated both the Due Process and Equal Protection Clauses. The ruling invalidated similar laws in roughly a dozen remaining states and established that racial classifications in law must survive the strictest judicial scrutiny.
Students for Fair Admissions v. Harvard
The equal protection debate came full circle in 2023. The Court ruled that race-conscious admissions programs at Harvard and the University of North Carolina violated the Fourteenth Amendment. For decades, universities had been allowed to consider an applicant’s race as one factor among many. The Court concluded that these programs used racial categories that were imprecise, relied on stereotyping, and had no meaningful endpoint.4Justia U.S. Supreme Court Center. Students for Fair Admissions Inc. v. President and Fellows of Harvard College, 600 U.S. ___ (2023) The decision effectively ended race-based affirmative action in college admissions, overruling precedents that had stood for over 40 years.
What the First Amendment Actually Protects
The First Amendment covers far more than spoken words. Some of the Court’s most interesting work has been deciding where protected expression ends and unprotected conduct begins.
Tinker v. Des Moines
In 1969, three Iowa students were suspended for wearing black armbands to protest the Vietnam War. The school had adopted a policy specifically banning the armbands after learning of the planned protest. The Court ruled 7–2 that students do not lose their constitutional rights at the schoolhouse gate. Schools can restrict student expression only when they can demonstrate it would substantially interfere with school operations or the rights of other students.5Justia U.S. Supreme Court Center. Tinker v. Des Moines Independent Community School District, 393 U.S. 503 (1969) Discomfort or disagreement with the message is not enough. The “substantial disruption” standard still governs public schools today.
Texas v. Johnson
Is burning an American flag protected speech? Gregory Lee Johnson set a flag on fire outside the 1984 Republican National Convention in Dallas as a political protest, and Texas convicted him under a flag desecration statute. In 1989, the Court overturned the conviction 5–4, holding that the government may not prohibit the expression of an idea simply because society finds it offensive.6Legal Information Institute. Texas v. Johnson, 491 U.S. 397 (1989) Congress tried twice afterward to pass a constitutional amendment banning flag burning, and failed both times.
Citizens United v. FEC
The Court ruled in 2010 that corporations and unions have First Amendment rights to spend money on independent political communications, and that the government cannot restrict those expenditures based on the speaker’s corporate identity.7Justia U.S. Supreme Court Center. Citizens United v. Federal Election Commission, 558 U.S. 310 (2010) The decision struck down a key provision of the Bipartisan Campaign Reform Act and opened the door to the super PACs that now dominate election spending. The case fundamentally altered how American elections are funded.
Rights You Have When Arrested
The Fifth and Sixth Amendments guarantee specific protections to anyone accused of a crime. Two cases from the 1960s turned those guarantees from abstract principles into concrete procedures that every police department and courthouse must follow.
Gideon v. Wainwright
Clarence Earl Gideon was charged with felony breaking and entering in Florida and asked the court for an attorney. The judge refused, because Florida law only provided free counsel in capital cases. Gideon represented himself, was convicted, and appealed from prison with a handwritten petition. In 1963, the Court ruled unanimously that the Sixth Amendment right to counsel is fundamental to a fair trial and that states must provide attorneys to defendants who cannot afford one.8Justia U.S. Supreme Court Center. Gideon v. Wainwright, 372 U.S. 335 (1963) The public defender systems that now exist across the country trace directly to this decision.
Miranda v. Arizona
Ernesto Miranda confessed to kidnapping and assault during a two-hour police interrogation. He was never told he had the right to remain silent or the right to a lawyer. In 1966, the Court threw out his confession, holding that the inherently coercive atmosphere of a custodial interrogation requires police to inform suspects of their rights before questioning begins.9Justia U.S. Supreme Court Center. Miranda v. Arizona, 384 U.S. 436 (1966) Those warnings include the right to remain silent, the warning that anything said can be used in court, and the right to an attorney. When police skip these steps, the resulting statements are generally inadmissible.
The Right to Privacy and Its Limits
The Constitution never mentions the word “privacy.” The Court had to find it, build on it, and in one recent case, pull much of that structure down.
Griswold v. Connecticut
Connecticut had a law making it a crime to use contraceptives, even for married couples. In 1965, the Court struck it down by reasoning that several amendments in the Bill of Rights cast “penumbras,” shadows of protection, that together create zones of privacy the government cannot enter. Justice Douglas’s majority opinion traced these zones through the First, Third, Fourth, Fifth, and Ninth Amendments.10Justia U.S. Supreme Court Center. Griswold v. Connecticut, 381 U.S. 479 (1965) The underlying principle, that the government needs a compelling reason before it can reach into your private life, became the foundation for decades of liberty-based rulings.
Lawrence v. Texas
In 2003, the Court struck down a Texas law criminalizing consensual sexual conduct between same-sex partners. The Court held that the liberty protected by the Due Process Clause gives adults the right to make intimate personal choices without government interference, and that the state cannot criminalize private consensual conduct simply because the majority disapproves of it.11Justia U.S. Supreme Court Center. Lawrence v. Texas, 539 U.S. 558 (2003) The decision overruled a 1986 case that had upheld similar laws and signaled a shift in how the Court viewed the government’s authority to enforce moral codes through criminal law.
Obergefell v. Hodges
In 2015, the Court held 5–4 that same-sex couples have a fundamental right to marry under both the Due Process and Equal Protection Clauses of the Fourteenth Amendment. Justice Kennedy’s majority opinion described marriage as “a keystone of the Nation’s social order” and concluded that excluding same-sex couples from it denied them equal dignity.12Legal Information Institute. Obergefell v. Hodges, 576 U.S. 644 (2015) The ruling invalidated same-sex marriage bans in every state that still had them and drew a direct line back to Loving v. Virginia.
Dobbs v. Jackson Women’s Health Organization
For nearly 50 years, the constitutional right to an abortion rested on the privacy framework established in Griswold and applied in Roe v. Wade (1973). In 2022, the Court overturned that framework. Dobbs held that the Constitution does not confer a right to abortion and returned the authority to regulate it to state legislatures.13Justia U.S. Supreme Court Center. Dobbs v. Jackson Women’s Health Organization, 597 U.S. ___ (2022) The majority concluded that Roe and the 1992 case Planned Parenthood v. Casey were “egregiously wrong.” Under the new standard, state abortion laws need only satisfy rational basis review, the lowest level of judicial scrutiny.
The practical consequences were immediate. Roughly a dozen states had “trigger laws” designed to ban or severely restrict abortion the moment Roe fell, and they took effect within days or weeks. Other states moved to expand abortion access. The result is a patchwork of laws that varies enormously by state. Dobbs also demonstrated that even long-standing constitutional precedents can be reversed, raising questions about the durability of other rights built on similar reasoning.
Guns in the Home and in Public
For most of American history, the Second Amendment was treated as a collective right tied to state militias, not an individual guarantee. Two recent cases changed that understanding entirely.
District of Columbia v. Heller
Washington, D.C., had one of the strictest gun laws in the country: a near-total ban on handgun possession in the home and a requirement that any lawfully owned firearm be kept disassembled or trigger-locked. In 2008, the Court struck down the ban, holding for the first time that the Second Amendment protects an individual right to possess a firearm for self-defense, unconnected to militia service.14Justia U.S. Supreme Court Center. District of Columbia v. Heller, 554 U.S. 570 (2008) Justice Scalia’s majority opinion emphasized that the right is not unlimited. Governments can still prohibit felons from carrying weapons, ban guns in sensitive places like schools and government buildings, and regulate commercial sale.
New York State Rifle and Pistol Association v. Bruen
Heller addressed guns in the home. Bruen, decided in 2022, extended the right to carrying firearms in public. New York required anyone seeking a concealed carry permit to demonstrate a special need for self-defense beyond what an ordinary citizen faces. The Court struck down that requirement and established a new test for evaluating all gun regulations: when the Second Amendment’s text covers the conduct, the regulation is presumptively unconstitutional unless the government can show it is consistent with the nation’s historical tradition of firearm regulation.15Justia U.S. Supreme Court Center. New York State Rifle and Pistol Association Inc. v. Bruen, 597 U.S. ___ (2022) The “history and tradition” test has sent lower courts through centuries of colonial and founding-era gun laws to determine which modern regulations survive, producing inconsistent results and ongoing litigation across the country.
Voting Rights After Shelby County
The Voting Rights Act of 1965 required states and counties with a history of racial discrimination in voting to get federal approval, known as “preclearance,” before changing their election laws. For decades, this was the most effective tool for preventing discriminatory voting practices. In 2013, the Court gutted it. Shelby County v. Holder struck down the formula that determined which jurisdictions were subject to preclearance, on the grounds that it relied on data from the 1960s and 1970s that no longer reflected current conditions.16Justia U.S. Supreme Court Center. Shelby County v. Holder, 570 U.S. 529 (2013) The Court left the preclearance requirement itself on the books but rendered it unenforceable by eliminating the coverage formula. Congress could theoretically pass a new formula based on current data, but hasn’t done so. Within hours of the ruling, several states began implementing voter ID laws and other restrictions that had been blocked under preclearance.
Presidential Power and the Administrative State
Three cases, spread across 50 years, define what Presidents and federal agencies can and cannot do.
United States v. Nixon
In 1974, a special prosecutor subpoenaed tape recordings of President Nixon’s conversations as evidence in the Watergate criminal investigation. Nixon invoked executive privilege, claiming that all presidential communications were confidential and beyond the reach of the courts. The Court unanimously rejected that argument. The justices acknowledged that a qualified executive privilege exists, but held that it cannot override the needs of a criminal trial when no military or diplomatic secrets are at stake.17Justia U.S. Supreme Court Center. United States v. Nixon, 418 U.S. 683 (1974) Nixon turned over the tapes and resigned within weeks.
Trump v. United States
Fifty years later, the Court revisited presidential power from a different angle. The question was whether a former President can be criminally prosecuted for actions taken while in office. The Court drew a new line in 2024: a former President has absolute immunity for actions within his core constitutional authority, presumptive immunity for all other official acts, and no immunity at all for unofficial conduct.18Justia U.S. Supreme Court Center. Trump v. United States, 603 U.S. ___ (2024) Lower courts are still working through the framework.
Loper Bright Enterprises v. Raimondo
Also in 2024, the Court overruled one of the most consequential administrative law doctrines of the past 40 years. Since 1984, under a framework known as Chevron deference, courts had been required to accept a federal agency’s interpretation of an ambiguous statute as long as the interpretation was reasonable. The Court held that this approach violated the Administrative Procedure Act, which directs courts to “decide all relevant questions of law” when reviewing agency actions.19Justia U.S. Supreme Court Center. Loper Bright Enterprises v. Raimondo, 603 U.S. ___ (2024) Federal agencies now face a judiciary that will second-guess their readings of environmental, financial, health, and labor regulations rather than deferring to agency expertise. The shift in power from the executive branch to the courts is unmistakable.