Courts resolve concrete disputes, interpret federal law, protect legal rights, and define the boundaries of government authority.
A layered system
Most federal cases begin in U.S. district courts. Appeals generally go to one of the regional courts of appeals. The Supreme Court chooses a small share of cases through petitions for writs of certiorari and also has limited original jurisdiction.
Judicial review
The Constitution does not use the phrase “judicial review,” but the practice became foundational: courts may decline to enforce government action they find inconsistent with the Constitution. Courts also review agency action and interpret federal statutes.
Judicial independence
Article III judges are nominated by the president, confirmed by the Senate, and ordinarily hold office during good behavior. Their compensation cannot be reduced while they remain in office. These protections seek to insulate legal judgment from immediate political pressure.
What courts cannot do
Federal courts require jurisdiction and an actual case or controversy. They do not issue general advisory opinions. They depend on litigants, lawyers, facts, procedural rules, and ultimately other institutions to implement many judgments.