Common law formed the basis for the U.S. legal system, which evolved to incorporate the U.S. Constitution, court precedent, local statues and regulations, and other sources as well. Common law arose in England and was then exported to the various British colonies around the world, including those in North America that would eventually become the United States. In the 1760s, Sir William Blackstone, a noted English legal scholar, wrote a highly detailed and comprehensive four-volume overview of common law titled Commentaries on the Laws of England. The collection became the basis for the study of law in English- speaking countries. It was used to train lawyers and to guide judges as they reviewed cases.