The Constitution of the United States gives ultimate power to the people, not to the government.
The Constitution created a government structure known as federalism, which requires the sharing of power between the federal government and the governments of each of the 50 states.
Under federalism, there are two types of court systems—federal and state. Federal courts have jurisdiction over issues mentioned or implied in the Constitution. The state courts have jurisdiction over matters not mentioned in the Constitution and those not specifically denied to the states by the Constitution.

The Constitution established three branches of government - the legislative, executive, and judicial. Courts are the judicial branch. As a co-equal branch of government, the judicial Branch is independent of the legislative and executive branches. Courts have the authority to interpret the law based on the Constitution without pressure from the other two branches.
Federal courts have the power of judicial review. This means they can review acts of Congress and actions of the President to ensure that they are permitted by the Constitution. If they are not, the Supreme Court of the United States declares such acts or actions unconstitutional, and they do not have the force of law.
The federal courts hear both civil and criminal cases. Civil cases involve disputes between private individuals, such as contract disputes. Criminal cases involve offenses against the whole community or society, such as murder. Courts follow different procedures in civil and criminal cases.
Within the federal and state court systems, there are two levels—trial courts and appellate courts. Trial courts, called U.S. District Courts, are courts of original jurisdiction. They are the first courts to hear either a civil or criminal case. If parties are not satisfied with the decision of a trial court, they may ask an appellate court, called a U.S. Circuit Court of Appeals, to review the trial court decision.
If parties are not satisfied with the decision of the U.S. Circuit Court of Appeals, they may appeal to the Supreme Court of the United States. The Supreme Court selects the cases it will hear. The Supreme Court is the final interpreter of the U.S. Constitution because it is the highest court in the land.
In addition to the judges, many other people work together to ensure the success of the judicial system. These include court staff, U.S. attorneys, federal public defenders, lawyers in private practice, and U.S. Marshals.
Citizens play a crucial role in the American judicial system. They help to ensure the fair and impartial administration of justice by participating directly in the work of the courts as jurors, witnesses, and court system employees. However, the central role that citizens play in ensuring the rule of law is using courts to settle disputes peacefully and abiding by court orders.