Laws serve five main functions in a democratic society. They offer security, supply predictability, provide for conflict resolution through the courts, reinforce society’s values, and provide for the distribution of social costs and benefits. American law is based on legislation, but its practice has evolved from a common law tradition and the use of precedent by judges.

Laws serve many purposes and are classified in different ways. Substantive law covers what we can or cannot do, while procedural law establishes the procedures used to enforce law generally and guarantees us procedural due process. Criminal law concerns specific behaviors considered undesirable by the government, while civil law covers interactions between individuals. Constitutional law refers to laws included in the Constitution as well as the precedents established over time by judicial decisions relating to these laws. Statutory law, administrative law, and executive orders are established by Congress and state legislatures, the bureaucracy, and the president, respectively.

The founders were deliberately vague in setting up a court system so as to avoid controversy during the ratification process. The Constitution never stated that courts could decide the constitutionality of legislation. The courts gained the extraconstitutional power of judicial review when Chief Justice John Marshall created it in Marbury v. Madison.

The United States has a dual court system, with state and federal courts each having different jurisdictions. Cases come directly to a court through its original jurisdiction or on appeal if it has appellate jurisdiction. Both court systems have three tiers; the federal courts range from district courts to the U.S. courts of appeals to the Supreme Court. Judges are appointed to the federal courts by a political process involving the president and the Senate and, often, the principle of senatorial courtesy.

The U.S. Supreme Court reigns at the top of the American court system. It is a powerful institution, revered by the American public but as political an institution as the other two branches of government. Politics is involved in how the Court is chosen—a process that considers merit; ideology, especially focusing on whether the justices are believers in strict constructionism, judicial interpretivism, judicial activism, or judicial restraint; reward; and representation. The work of the Court is also political, as the justices decide whether to issue writs of certiorari based on the application of the Rule of Four, and decide cases influenced by their own values, the solicitor general, and a variety of amicus curiae briefs. These influences show up in the writing of the opinion, and both concurring and dissenting opinions. These opinions are decisive in determining who gets what in American politics.