Judicial review is the power of courts to decide whether a government action is lawful. In the United States, that usually means asking whether a statute, executive action, agency rule, prosecution, search, election rule, or official decision conflicts with the Constitution or another controlling law.

The Constitution gives federal courts “the judicial power,” but it does not use the exact phrase “judicial review.” The doctrine became central after Marbury v. Madison and later cases. Courts exercise this power through real cases, not general advisory opinions.

Judicial review can protect constitutional rights, limit unlawful agency action, interpret ambiguous statutes, resolve conflicts between governments, and set rules that affect schools, elections, policing, speech, religion, property, immigration, health, and economic regulation.

Courts do not simply review every political disagreement. A case usually needs jurisdiction, standing, a live controversy, a legal claim, a record, and a remedy the court can grant. Appeals courts often review legal issues rather than retrying facts. Supreme Court review is discretionary in most cases.

Judicial review is not just an abstract court power. It can decide whether a law applies, whether an agency exceeded its authority, whether a prosecution violated rights, whether a school or local government acted lawfully, or whether a regulation can continue. Courts usually do not review a question in the abstract. A person, organization, government, or business must bring a real dispute that the court has power to hear.

When reading about judicial review, look for the legal question, the court that decided it, the statute or constitutional provision involved, the remedy, and whether higher courts can still review the case. Those details tell you whether the decision changes national law, affects only the parties, or begins a longer legal path.