The annotations are provided by the editors and are not a part of the official language of the code. United States Code Annotated , published by West, is an annotated version of the official United States Code published by the federal government. Most annotated codes are statutory. There are very few annotated regulatory codes.
Secondary authority are sources which explain the law.
These may be law review articles, scholarly treatises, bar journals, encyclopedias or practitioner books. Whether a statute or regulation is mandatory authority may depend on the facts involved. Mandatory case law may also depend on the identical nature of the facts and legal issues involved as well as the level of the court which issued the opinion. A lower court is required to follow a higher court's ruling on an issue. A higher court is not required to follow the ruling or reasoning of a lower court opinion, although that opinion may be persuasive authority.