The landmark Supreme Court cases below are the decisions that built American constitutional law and still govern how it works. They answer a handful of durable questions: who gets to say what the Constitution means, how far federal and state power reach, what the President can do, which rights the Fourteenth Amendment protects, where free speech ends, what police must do before they search or question you, whether the Second Amendment protects individuals, and how much power federal agencies hold. Each case below settled or reshaped one of those questions.
Judicial Review and the Federal-State Balance
Every other power the Court exercises traces back to Marbury v. Madison (1803). A newly appointed judge sued to force delivery of his commission after a change in administration. Chief Justice John Marshall ruled that the provision of the Judiciary Act of 1789 giving the Court authority to hear the case expanded its original jurisdiction beyond what Article III allows, and he struck it down. That was the first time the Court invalidated an act of Congress, and it established judicial review as the mechanism that makes the Constitution enforceable against ordinary legislation.1Justia U.S. Supreme Court Center. Marbury v. Madison
McCulloch v. Maryland (1819) tested how far Congress could stretch its lawmaking power. Maryland had taxed the Second Bank of the United States, arguing the Constitution never explicitly authorized Congress to charter a national bank. The Court disagreed, holding that Congress has implied powers through the Necessary and Proper Clause: if the end is legitimate and within the Constitution’s scope, Congress may use reasonable means to reach it. The Court also held that states cannot tax or obstruct legitimate federal operations.2Justia. McCulloch v. Maryland, 17 US 316
Gibbons v. Ogden (1824) extended federal reach over the national economy. New York had granted a steamboat monopoly in its waters, but a competing operator held a federal coastal-trade license. The Court sided with the federal licensee and read “commerce” broadly to include navigation and the movement of goods and people across state lines. Under the Commerce Clause, Congress holds authority over interstate commercial activity, and conflicting state laws fall.3Legal Information Institute. Gibbons, Appellant, v. Ogden, Respondent Those three early rulings still frame the balance between state and federal power.
Limits on Presidential Power
Youngstown Sheet and Tube Co. v. Sawyer (1952) is the foundational modern case on executive authority. During the Korean War, President Truman seized private steel mills to head off a strike that would have disrupted military production. The Court held the seizure unconstitutional because Congress had not authorized it, and the President’s commander-in-chief power does not extend to taking over private industry at home.4GovInfo. Youngstown Sheet and Tube Co. v. Sawyer Justice Jackson’s concurrence sorted presidential power into three zones: strongest with congressional approval, uncertain when Congress is silent, weakest against Congress’s expressed will. Courts still use that framework.
United States v. Nixon (1974) answered whether a sitting President can refuse to produce evidence in a criminal investigation by invoking executive privilege. President Nixon had been subpoenaed for Watergate tape recordings. The Court unanimously acknowledged that executive privilege exists and protects confidential presidential communications, but held it is not absolute. A generalized claim of confidentiality must give way to the justice system’s need for evidence in a criminal trial.5Justia. United States v. Nixon Nixon resigned two weeks later.
Trump v. United States (2024) moved the line the other direction. The Court held that a former President has absolute immunity from criminal prosecution for actions within his core constitutional authority, such as the pardon power or command of the military. Other official acts receive at least presumptive immunity, which prosecutors face a heavy burden to overcome. Unofficial acts get no immunity.6Legal Information Institute. Trump v. United States It was the first time the Court recognized broad criminal immunity for presidential conduct, and it drew sharp dissents.
Equal Protection and Civil Rights
The Fourteenth Amendment forbids states to deny any person equal protection under the law.7Congress.gov. US Constitution – Fourteenth Amendment For over fifty years after ratification, that guarantee coexisted with state-enforced segregation. In Plessy v. Ferguson (1896), the Court upheld a Louisiana law requiring separate railway cars for Black and white passengers, reasoning that separation alone did not imply legal inequality so long as the facilities were equivalent. The “separate but equal” doctrine gave constitutional cover to segregation in schools, hospitals, restaurants, and public spaces across the country.
Brown v. Board of Education (1954) dismantled that framework. The Court unanimously held that separate educational facilities are inherently unequal and deny equal protection under the Fourteenth Amendment.8Justia. Brown v. Board of Education of Topeka, 347 US 483 A follow-up ruling directed desegregation to proceed “with all deliberate speed,” opening decades of legal battles over school integration and energizing the broader civil rights movement.
Loving v. Virginia (1967) carried equal protection into personal life. Virginia and fifteen other states still banned interracial marriage. The Lovings, a Black woman and white man, were convicted under Virginia’s anti-miscegenation statute. The Court struck the law down unanimously, holding that racial classifications in marriage laws served no purpose beyond maintaining white supremacy and violated both the Equal Protection and Due Process Clauses.9Justia. Loving v. Virginia The decision also classified marriage as a fundamental right under the Fourteenth Amendment.
Students for Fair Admissions v. President and Fellows of Harvard College (2023) marked the Court’s most recent major turn on race. The majority struck down race-conscious admissions programs at Harvard and the University of North Carolina, holding that the programs violated the Equal Protection Clause because they used racial categories that were overbroad and lacked a meaningful connection to their stated educational goals. The ruling did not bar applicants from discussing how race shaped their experiences in essays, but it ended the use of race as a factor in admissions formulas.10Justia. Students for Fair Admissions, Inc. v. President and Fellows of Harvard College
Substantive Due Process and Privacy
The Fourteenth Amendment also protects “liberty” from government interference without due process of law, and the Court has read that word to cover rights the Constitution never names.11Congress.gov. Overview of Substantive Due Process This doctrine, called substantive due process, has produced some of the Court’s most consequential and contested decisions.
Griswold v. Connecticut (1965) was the breakthrough. Connecticut had long criminalized the use of contraceptives. The Court struck the law down, holding that several provisions in the Bill of Rights create overlapping zones of privacy the government cannot invade, and that the right of married couples to make reproductive decisions fell within them. Constitutional privacy had its first real foothold.
Roe v. Wade (1973) extended that privacy right to a woman’s decision to end a pregnancy. The Court adopted a trimester framework: in the first trimester the decision belonged to the woman and her doctor; in the second, the state could regulate the procedure to protect maternal health; after viability in the third, the state could restrict abortion entirely except where the woman’s life or health was at stake.12Justia. Roe v. Wade, 410 US 113 The ruling stood for nearly fifty years.
Dobbs v. Jackson Women’s Health Organization (2022) overruled Roe entirely. The majority held that the Constitution does not confer a right to abortion and that for a right to be protected under substantive due process, it must be deeply rooted in the nation’s history and traditions.13Supreme Court of the United States. Dobbs v. Jackson Women’s Health Organization Authority over abortion regulation returned to state legislatures, producing a patchwork of laws almost overnight.
Obergefell v. Hodges (2015) recognized same-sex marriage as a fundamental right under both the Due Process and Equal Protection Clauses, holding that the right to marry is so central to personal autonomy that states cannot deny it to same-sex couples.14Justia. Obergefell v. Hodges, 576 US 644 The Dobbs majority expressly distinguished abortion from other substantive due process rights like marriage, though Justice Thomas’s concurrence suggested the Court should reconsider those precedents too.
Freedom of Expression and the First Amendment
The First Amendment bars Congress from restricting freedom of speech or the press, and the Court has spent more than a century working out what those protections actually cover.15Congress.gov. Constitution of the United States – First Amendment
Schenck v. United States (1919) was an early attempt to draw the line. The defendants had distributed pamphlets urging resistance to the World War I draft. Justice Oliver Wendell Holmes, writing for a unanimous Court, upheld their convictions and introduced the “clear and present danger” test: speech can be restricted when it poses an immediate risk of serious harm Congress has power to prevent.16Legal Information Institute. Schenck v. United States Later cases refined and largely replaced the test, but it fixed the idea that free speech has boundaries.
Tinker v. Des Moines (1969) tested those boundaries inside public schools. Students were suspended for wearing black armbands to protest the Vietnam War. The Court held that students do not lose their constitutional rights at the schoolhouse gate and that school officials cannot suppress student expression unless it causes a material and substantial disruption to the educational environment.17Justia. Tinker v. Des Moines Independent Community School District
New York Times Co. v. United States (1971) addressed the most aggressive form of restriction: stopping publication before it happens. The Nixon administration sought to block the Times and the Washington Post from publishing the Pentagon Papers, a classified study of U.S. involvement in Vietnam. The Court ruled that the government bears an extraordinarily heavy burden when seeking prior restraint on the press, and it had not met that burden.18Justia. New York Times Co. v. United States
Kennedy v. Bremerton School District (2022) reshaped how courts evaluate government-sponsored religious expression. A public school football coach was disciplined for praying on the field after games. The Court ruled in his favor and replaced the longstanding Lemon test for Establishment Clause cases with a standard rooted in historical practices and understandings, asking whether government conduct involving religion is consistent with how the Founding generation understood church-state relations.19Justia. Kennedy v. Bremerton School District
Criminal Procedure and Rights of the Accused
The Bill of Rights devotes more text to protecting people accused of crimes than to almost any other subject, and the Court has spent decades applying those protections to the states.
Mapp v. Ohio (1961) established the exclusionary rule for state courts. Police had forced their way into a home without a valid warrant and seized materials used to convict the occupant. The Court held that evidence obtained through an unconstitutional search cannot be used at trial, applying the Fourth Amendment to state prosecutions for the first time.20Justia. Mapp v. Ohio, 367 US 643
Gideon v. Wainwright (1963) guaranteed counsel to defendants who cannot afford one. Clarence Earl Gideon was charged with a felony in Florida and asked the court for an attorney. The judge refused, and Gideon represented himself and lost. The Supreme Court reversed, ruling that the Sixth Amendment requires states to provide attorneys for defendants who cannot pay in any case where imprisonment is at stake.21Justia. Gideon v. Wainwright The decision created the public defender system as we know it.
Miranda v. Arizona (1966) is probably the most culturally familiar of all Supreme Court decisions. Police had interrogated Ernesto Miranda for hours without telling him he could remain silent or have a lawyer present, and his confession led to a conviction. The Court held that before any custodial interrogation, law enforcement must inform suspects of their right to remain silent and their right to an attorney, and statements obtained without those warnings are inadmissible.22Justia U.S. Supreme Court Center. Miranda v. Arizona, 384 US 436
Digital-Era Fourth Amendment
Riley v. California (2014) held unanimously that police generally need a warrant before searching the digital contents of a cell phone seized during an arrest. The Court reasoned that the volume of personal data on a modern phone implicates far greater privacy interests than a search of pockets or a wallet, and the traditional justifications for warrantless searches during arrest, like officer safety, do not apply to digital data.23Justia. Riley v. California
Carpenter v. United States (2018) extended warrant protection to cell-site location records held by wireless carriers. The government had obtained 127 days of a suspect’s location history without a warrant under a statute requiring less than probable cause. The Court held that accessing that kind of detailed, long-term location data is a search under the Fourth Amendment, and the government must generally get a warrant before compelling a carrier to turn it over.24Supreme Court of the United States. Carpenter v. United States
The Second Amendment
For most of American history, the Second Amendment was understood primarily as a collective right tied to state militias. District of Columbia v. Heller (2008) changed that. The case challenged a D.C. law that effectively banned handgun possession in the home. The Court held that the Second Amendment protects an individual right to possess firearms for lawful purposes like self-defense, independent of militia service.25Justia. District of Columbia v. Heller The majority emphasized that this right is not unlimited; restrictions on felons possessing weapons, carrying guns in sensitive locations, and banning dangerous or unusual weapons remain permissible.
New York State Rifle and Pistol Association v. Bruen (2022) set the test courts must use when evaluating gun regulations. New York required residents to demonstrate a special need for self-defense before obtaining a permit to carry a handgun in public. The Court struck that requirement down and held that when the Second Amendment’s text covers the conduct, the government can only justify a regulation by showing it is consistent with the nation’s historical tradition of firearm regulation.26Justia. New York State Rifle and Pistol Association, Inc. v. Bruen This history-and-tradition test replaced the means-end scrutiny lower courts had used for over a decade, and it has produced significant uncertainty about which modern gun laws can survive.
Federal Agency Power
Federal agencies write the regulations that touch nearly every part of daily life, from food safety to air quality to financial markets. For forty years, courts largely deferred to agency interpretations of the laws they administer. Two recent decisions shifted that balance.
West Virginia v. EPA (2022) introduced the major questions doctrine as a formal limit on agency power. The EPA had adopted a rule designed to shift electricity generation away from coal-fired plants toward cleaner sources. The Court held that when an agency claims authority to make decisions of vast economic and political significance, it needs clear congressional authorization. Without an unmistakable statement from Congress, an agency cannot claim sweeping new regulatory power based on a broad reading of an old statute.27Supreme Court of the United States. West Virginia v. EPA
Loper Bright Enterprises v. Raimondo (2024) went further and overruled Chevron outright. Since 1984, Chevron had directed courts to defer to an agency’s reasonable interpretation of an ambiguous statute. The Court held that the Administrative Procedure Act requires judges to exercise their own independent judgment when deciding whether an agency has acted within its legal authority. Courts can no longer uphold an agency interpretation simply because the underlying statute is unclear.28Justia. Loper Bright Enterprises v. Raimondo Agencies can still offer interpretations, and courts may find them persuasive, but deference is no longer automatic. The practical effect is that regulated industries and advocacy groups now have a stronger hand challenging agency rules in court, and the outcome of regulatory disputes depends more on how judges read the statute than on what the agency thinks it means.