Copyright status of work by the U.S. government

Anything that is written as "a work prepared by an officer or employee" of the United States federal government "as part of that person's official duties," is permitted to be used without a penalty and is in the public domain. More details of this rule, as defined by the United States copyright law of the United States copyright law, is available. Such writings are not protected under U.S. law. This rule may not be true in other countries.