Some works that might qualify for copyright protection are instead part of the public domain. The public has the full rights to use these work without obtaining permission and no one can come to control those rights in the future.
There are three common ways that works enter the public domain:
1. The copyright has expired.
Probably the most common category of public domain works is those for which copyright has expired. Identifying these works is complicated by the fact that the term of copyright has varied over time and for different types of work. One useful fact is that any works published in the U.S. before 1923 will be part of the public domain.
2. The owner of the copyright did not follow a formal requirement to give the work copyright protection.
Before March 1, 1989, creators had to take proactive steps to arrange for their works to be protected by copyright. If they did not take those steps, the work entered the public domain. Many works created from 1923 to 1989 are in the public domain, but more information than the publication date is needed in order to make that determination.
3. The copyright owner deliberately places it in the public domain (this includes U.S. government works).
Some copyright owners decide to place their work in the public domain. For example, any works created by the United States Government including: federal judicial decisions, federal statutes, speeches of federal government officials given in the course of their employment, federal government press releases, and federal government reports (such as census reports) are placed in the public domain and their use is not limited by copyrights. The practices of state and local governments vary widely and can change over time so must be investigated on a case-by-case basis.