is the original legal system, based on court decisions, that originated in England and was brought over to the United States when it was first forming. United States common law varies by state, the three types are: English; French; and Spanish.
Merriam-Webster Online Dictionary
common law (noun) the body of law developed in England primarily from judicial decisions based on custom and precedent, unwritten in statute or code, and constituting the basis of the English legal system and of the system in all of the United States except Louisiana