1. What is common law?
U.S. legal system was formed under the laws of the Anglo-Saxon legal family, so the main source of law it is considered a legal precedent. Precedent called the court's decision in a particular case shall become effective source of law, which is receiving the ability to set, modify or revoke the legal norms. U.S. common law suggests the existence of a hierarchy of precedents on which decisions taken by higher courts is binding in cases before the lower courts.
U.S. common law system is in constant motion; it is created and is directly determined by the judges making decisions on this or other matters. Adopted a decision in a particular case in the future become applicable to other cases of a similar nature. It often happens that judges face a lack of clear definitions in the law. In these cases the law gives them authority to the U.S. and even enjoins upon themselves to define the legal norms, creating precedents. In aggregate weight of precedents called common law, court decisions predetermine certain categories of cases. In the future, when considering the various cases in the event of disagreement with the views of the parties of the law, the judge considers the case in accordance with the provisions of the previous precedent on a similar process. If such a dispute had already been considered in court, and it was a final decision, the judges are required to follow the arguments used in the previous solutions. The court may determine that the essence of the case is different from the one that was in the previous processes. Then the solution in this case will be taken in consideration for the first time. The decision taken will also be considered as a precedent.
2. What are the sources of American law?
In the more than 200 years since the founding of the United States and adoption of the English common law, the lawmakers of this country have developed a substantial body of law. (Cheeseman 12) Sources of law include:

1.Common Law,(Case Law) – described below 2.Statutory Law - The legislative branch is responsible for creation of law. Legislature possesses the authority to modify, abolish or adopt the common law, in whole or in part. During the 19th century, states began a major movement away from the common law and instead began codifying the law. Although the power of the legislative branch is significant, there are limits. The constitutions of the United States and of the many states contain limits on such state and federal authority. Most of these limits are found in the Bill of Rights. (Sources of American Law) 3. Administrative Law - regulates the base legal provisions and procedures of administrative agencies, as well as control over the administration of the courts. Emphasis in administrative law of the country focuses on the relationship of these institutions to individuals, i.e. on “external administrative law.” Unlike the latter, the 'internal administrative law" regulates the internal administrative structure and the relationship between its constituent parts. Americans are interested in it only to the extent that it provides legal assistance to individuals. Therefore, administrative law in the United States is considered mainly as a legal industry, designed to protect individuals from the tyranny of bureaucracy, public administration. 4.Court Rules - Most court rules are drafted under the direction of the highest court of the state and become effective either by vote of the court or after being presented to the state legislature for ratification. In the federal system, the rules are drafted by the Judicial Conference, under the direction of the Supreme Court, and then presented to Congress. If Congress fails to act to nullify the rules, they become law. (Sources of American Law) 5.Constitutional Law - is a complex system, which is a set of federal constitutional law and constitutional law states having considerable originality. First U.S. Constitution was supplemented