10 Most Important Constitutional Law Cases Every Law Student Must Know

The single most important case in American constitutional law. Chief Justice Marshall established the power of judicial review, holding that the Supreme Court has authority to strike down laws that conflict with the Constitution. Marbury is the foundation of the entire American system of constitutional adjudication.

The foundational case on federal powers and the Necessary and Proper Clause. Marshall held that Congress has implied powers beyond those enumerated in the Constitution and that states cannot tax federal instrumentalities. McCulloch defines the scope of federal power and the supremacy of federal law.

The first major Commerce Clause case. Marshall broadly defined 'commerce among the several States' to include navigation and commercial intercourse, establishing that Congress's power to regulate interstate commerce is plenary. Gibbons set the stage for the modern expansion of federal regulatory authority.

The defining case of the substantive due process era. The Court struck down a maximum-hours law for bakers, finding it violated liberty of contract under the Due Process Clause. Though later repudiated, Lochner remains central to understanding judicial activism, the limits of substantive due process, and the debate over unenumerated rights.

The landmark First Amendment case on defamation and freedom of the press. The Court held that public officials must prove 'actual malice' -- knowledge of falsity or reckless disregard for truth -- to recover damages for defamation. Sullivan constitutionalized defamation law and is essential to understanding press freedom.

The controlling case on incitement and the limits of free speech. The Court held that the government cannot punish inflammatory speech unless it is directed to inciting imminent lawless action and is likely to produce such action. Brandenburg replaced the 'clear and present danger' test and defines the modern boundary of protected speech.

One of the most consequential substantive due process cases. The Court recognized a constitutional right to abortion under the right to privacy, establishing a trimester framework. Though later overruled by Dobbs v. Jackson (2022), Roe remains essential for understanding unenumerated rights, substantive due process, and the evolution of constitutional interpretation.

The high-water mark of Commerce Clause power. The Court upheld federal regulation of wheat grown for personal consumption, holding that even purely local activity can be regulated if, in the aggregate, it substantially affects interstate commerce. Wickard defines the outer reach of federal regulatory authority under the Commerce Clause.

The Court held that same-sex couples have a fundamental right to marry under the Due Process and Equal Protection Clauses of the Fourteenth Amendment. Obergefell is a modern landmark on substantive due process, equal protection, and the evolving understanding of fundamental rights.

The foundational case on separation of powers and presidential authority. The Court struck down President Truman's seizure of steel mills during the Korean War. Justice Jackson's concurrence created the three-category framework for analyzing presidential power that remains the controlling test for executive authority disputes.