The US Constitution establishes the three branches of the federal government and gives them the ability to check each other’s authority. The Judicial branch oversees the actions of the Executive and Legislative branches through judicial review to ensure that they do not violate the Constitution. While not perfect, the US federalist system was designed to restrain governmental power and to prevent the rise of an authoritarian regime.
The Judicial Branch is the only unelected branch of government. Marbury v. Madison established the doctrine of judicial review, which allows courts to determine the final validity of laws as well as the meaning of the Constitution. The president can check the judiciary through appointments and the pardon power. Congress can check the judiciary through confirming judges, administrative control of court calendars and funds, and legislation about the types of cases a court can hear.
There are fifty-six separate legal systems in the United States. Subject matter jurisdiction is the authority of a court to hear a case based on the type of dispute. State law claims are generally heard in state courts, while federal question cases are generally heard in federal court. Federal courts may hear state law claims under diversity jurisdiction. Federal cases are filed in a US District Court and appealed to a US Circuit Court of Appeals. State cases are typically filed in a trial court and appealed to an intermediate court of appeals.