Codification
Today, large portions of slip laws denominated as public laws are drafted as amendments to the United States Code. Once enacted into law, an Act will be published in the Statutes at Large and will add to, modify, or delete some part of the United States Code. Provisions of the public laws that contain only enacting clauses, effective dates, and similar matters are not generally codified. Private laws also are not generally codified.
Some portions of the United States Code have been enacted as positive law and other portions have not been so enacted. In case of a conflict between the text of the Statutes at Large and the text of a provision of the United States Code that has not been enacted as positive law, the text of the Statutes at Large takes precedence.
Read more about this topic: United States Statutes At Large