A law is unconstitutional when it conflicts with the U.S. Constitution, and courts, not legislatures, decide when that line has been crossed. Examples of unconstitutional laws run across almost every part of the Bill of Rights and the Fourteenth Amendment: statutes that punished flag burning, required school prayer, banned handguns in the home, let police search cell phones without a warrant, criminalized vague “loitering,” denied poor defendants a lawyer, imposed automatic life sentences on juveniles, seized property worth far more than the offense justified, and segregated public schools by race. The Supreme Court established its authority to strike down such laws in 1803 in Marbury v. Madison, declaring that “a legislative act contrary to the constitution is not law.”1Constitution Annotated. ArtIII.S1.3 Marbury v Madison and Judicial Review Once a court invalidates a statute, the unconstitutional portion loses legal force, though judges will often preserve the rest of the law if it still functions on its own.
How a Law Gets Struck Down
Courts do not go hunting for bad laws. Someone has to sue, and that person needs standing: a concrete personal injury, a direct link between the injury and the government action, and a realistic chance that a ruling would fix the problem.2Constitution Annotated. Overview of Standing Disagreement is not enough. The challenger has to show real harm.
Once a case is properly before a court, judges compare the law against the Constitution’s text and the prior decisions interpreting it. If only one provision is the problem, courts apply severability analysis, asking whether the rest of the statute still works without the offending piece. If it does, the court cuts out the bad part and leaves the rest standing.
The examples below show how that process has played out across different constitutional protections.
First Amendment: Speech and Religion
Punishing Flag Burning
In Texas v. Johnson (1989), the Supreme Court struck down a Texas law that criminalized burning the American flag as political protest.3Justia. Texas v Johnson The problem was not the physical act. The statute targeted the conduct because of the message behind it, which made it a content-based restriction on expression. When the government punishes behavior because of the idea it conveys, it is regulating speech, and content-based speech restrictions almost never survive constitutional review.
Censoring the Press Before Publication
Prior restraint, meaning a government order telling a publisher not to print something, carries what the Supreme Court has called “a heavy presumption against constitutional validity.”4Justia. The Doctrine of Prior Restraint The best-known example is the Pentagon Papers case, in which the Nixon administration tried to stop the New York Times from publishing classified Vietnam War documents. The Court rejected the national security argument because it did not meet the extraordinarily high burden required for pre-publication censorship. The constitutional remedy for harmful speech is almost always after-the-fact accountability, not a gag beforehand.
State-Written Prayers in Public Schools
The Establishment Clause bars government promotion of religion. In Engel v. Vitale (1962), the Supreme Court struck down a New York policy directing public school teachers to lead students in a state-composed morning prayer. The Court held that “it is no part of the business of government to compose official prayers for any group of the American people to recite as a part of a religious program carried on by government.”5Justia. Engel v Vitale Making participation voluntary did not save the policy. Government sponsorship of the prayer was the violation.
Second Amendment: Firearms
Banning Handguns in the Home
Washington, D.C. once had one of the strictest gun laws in the country, effectively barring residents from keeping handguns in their homes. In District of Columbia v. Heller (2008), the Supreme Court struck it down, holding that the Second Amendment “protects an individual right to possess a firearm unconnected with service in a militia, and to use that arm for traditionally lawful purposes, such as self-defense within the home.”6Library of Congress. District of Columbia et al v Heller, 554 US 570 (2008) Two years later, McDonald v. City of Chicago (2010) extended that protection to state and local laws, striking down Chicago’s similar ban.7Justia. McDonald v City of Chicago Both decisions noted the right has limits. Bans on felon possession, restrictions in schools and government buildings, and regulations on commercial sales remain constitutional.
Requiring “Proper Cause” to Carry
Some states required concealed carry applicants to prove a specific, heightened need for self-defense beyond what any ordinary person might face. In New York State Rifle & Pistol Association v. Bruen (2022), the Supreme Court struck down New York’s “proper cause” requirement, holding that it prevented ordinary law-abiding citizens from exercising their right to carry a handgun for self-defense outside the home.8Justia. New York State Rifle and Pistol Association Inc v Bruen States can still require permits based on objective criteria like background checks and training. What they cannot do is give officials open-ended discretion to decide who deserves to carry one.
Fourth Amendment: Searches and Seizures
Searching a Cell Phone Without a Warrant
Before Riley v. California (2014), police routinely searched the phones of people they arrested, treating them like any other object in a suspect’s pocket. The Supreme Court unanimously rejected that practice, holding that a warrant is required before searching the digital contents of a cell phone seized during an arrest.9Justia. Riley v California, 573 US 373 (2014) A modern smartphone holds years of photos, messages, browsing history, and location data. That is nothing like a wallet or a pack of cigarettes, and treating it that way would give police access to the most intimate details of a person’s life with no judicial check.
What Happens to Illegally Seized Evidence
Striking down a search as unconstitutional would mean little if prosecutors could still use whatever police found. In Mapp v. Ohio (1961), the Supreme Court held that “all evidence obtained by searches and seizures in violation of the Constitution is inadmissible in a state court.”10Justia. Mapp v Ohio Federal courts already followed this exclusionary rule. Mapp extended it to every courtroom in the country. The baseline requirement itself, probable cause before a government search, comes directly from the Fourth Amendment.11Constitution Annotated. Amdt4.5.3 Probable Cause Requirement
Fifth Amendment: Due Process and Property
Laws Too Vague to Follow
Due process requires that criminal laws be written clearly enough for an ordinary person to know what is illegal. When a statute is so ambiguous that people have to guess at its meaning, courts strike it down as “void for vagueness.”12Constitution Annotated. Overview of Void for Vagueness Doctrine Loitering ordinances are a repeat offender. A law that prohibits “wandering without a clear purpose” fails because it tells no one what a clear purpose actually looks like. That kind of language also hands police arbitrary arrest power and leaves judges with no consistent standard to apply.
Taking Property Without Just Compensation
The Takings Clause states that private property shall not “be taken for public use, without just compensation.”13Constitution Annotated. US Constitution – Fifth Amendment Eminent domain lets the government take land for roads, schools, and other projects, but the taking must serve a public purpose and the owner must receive fair market value. A seizure that skips payment, or pays well below market, violates the Fifth Amendment. Courts have interpreted “public use” broadly. In Kelo v. City of New London (2005), the Supreme Court allowed a city to take private homes and transfer the land to a private developer as part of an economic redevelopment plan.14Justia. Kelo v City of New London That ruling prompted many states to pass their own stricter limits, but it remains the federal standard.
Sixth Amendment: Right to Counsel
Denying a Lawyer to Someone Who Cannot Afford One
Before Gideon v. Wainwright (1963), some states provided lawyers only in capital cases. Clarence Gideon was charged with breaking into a Florida pool hall, asked for a lawyer, was refused, represented himself, and was convicted. The Supreme Court unanimously reversed, holding that “any person haled into court, who is too poor to hire a lawyer, cannot be assured a fair trial unless counsel is provided for him.”15Justia. Gideon v Wainwright That decision created the public defender systems that exist across the country today.
When Counsel Is So Ineffective It Violates the Constitution
Having a lawyer in the room is not enough if that lawyer does essentially nothing. Strickland v. Washington (1984) set a two-part test for ineffective assistance claims. The defendant must show that the attorney’s performance was objectively deficient, falling below what any reasonable lawyer would have done, and must also show prejudice, meaning a reasonable probability that the outcome would have been different with competent representation.16Justia. Strickland v Washington Courts are skeptical of hindsight attacks on trial strategy, but a lawyer who sleeps through testimony, skips obvious investigation, or misreads the governing law can render a conviction unconstitutional.
Eighth Amendment: Punishment and Fines
Automatic Life Without Parole for Juveniles
In Graham v. Florida (2010), the Supreme Court held that sentencing a juvenile to life without parole for a non-homicide offense is unconstitutional. States must provide “some meaningful opportunity for release based on demonstrated maturity and rehabilitation.”17Justia. Graham v Florida Miller v. Alabama (2012) went further, striking down mandatory life-without-parole sentences for juveniles even in homicide cases.18Justia. Miller v Alabama A judge can still impose that sentence after weighing the individual circumstances. An automatic sentencing scheme that ignores the offender’s age cannot stand.
Excessive Fines and Forfeitures
In Timbs v. Indiana (2019), the Supreme Court confirmed that the Eighth Amendment’s ban on excessive fines applies to state and local governments.19Justia. Timbs v Indiana Indiana had seized a $42,000 Land Rover through civil forfeiture after the owner was convicted of selling a small amount of drugs. The state argued the Excessive Fines Clause did not reach it at all. The Court unanimously disagreed. The decision matters most in civil forfeiture cases, where the value of the seized property can dwarf the underlying offense.
Fourteenth Amendment: Equal Protection
Racial Segregation in Public Schools
Brown v. Board of Education (1954) is the most recognized example of unconstitutional government action in American history. Many states required Black and white students to attend separate schools under the doctrine of “separate but equal.” The Supreme Court unanimously rejected that framework, holding that “separate educational facilities are inherently unequal” and that segregating public schools by race denies minority students equal protection of the laws.20Justia. Brown v Board of Education of Topeka The decision did not merely find the particular schools unequal in quality. It held that the act of separation itself violated the Fourteenth Amendment, regardless of how comparable the physical facilities might have been.
How Courts Judge Equal Protection Claims
Not every law that treats people differently is unconstitutional. Governments classify people constantly: by income for taxes, by age for voting and driving, by profession for licensing. The question is whether the classification has adequate justification, and courts apply different levels of scrutiny depending on who is being classified. Laws that distinguish based on race or national origin face strict scrutiny, the highest bar, and almost never survive. Classifications based on gender receive intermediate scrutiny, requiring the government to show the law serves an important objective and is substantially related to it. Most other classifications face only rational basis review, meaning the government needs just a plausible, legitimate reason. Which test applies often decides the case before the analysis even begins, which is why so many equal protection fights are really fights over the level of scrutiny.