the system of law in the united states is based on the english common law
At both the federal and state levels, with the exception of the state of Louisiana, the law of the United States is largely derived from the common law system of English law, which was in force at the time of the American Revolutionary War. However, American law has diverged greatly from its English ancestor both in terms of substance and procedure, and has incorporated a number of civil law innovations.
Law of the United States