If I make a list of the gravemarkers in a cemetery, will my list be protected by copyright? If I publish my genealogy file, will the publication have a copyright? If I publish a list of family names from the U.S. Census, will the list be copyrighted? The answer to all three questions is no unless you add your own original work to the product and even then, the public portions of the documents will not be subject to copyright.
U.S. Copyright Law, contained in Title 17 of the U.S. Code, provides that "works consisting entirely of information that is common property and containing no original authorship (for example: standard calendars, height and weight charts, tape measures and rulers, and lists or tables taken from public documents or other common sources)." Public documents and other such common sources are said to be in the "public domain." Works in the public domain include any works which are too old to have copyright protection. Some other reasons a work might be in the public domain include lack of proper notice, failure to renew, failure to comply with manufacturing requirements, being a sound recording fixed prior to U.S. protection, and lack of national eligibility, that is, the source nation and the United States did not then have a treaty relationship. One huge area of copyright exemption is anything produced by the U.S. government. See Section 105 of Title 17. Copyright protection is not available for any work of the United States Government, but the United States Government is not precluded from receiving and holding copyrights transferred to it by assignment, bequest, or otherwise.
Whether or not a work, including genealogical compilations is subject to copyright can be a very complicated question. The law has changed considerably over time in the U.S. as well as in other countries. Generally, you cannot take information or works in the public domain and make them subject to copyright protection.
So, looking at a genealogy file, very little of the information, unless of original authorship by the compiler, would be considered subject to copyright. In copyright law, there is a big difference between writing a history of your family using your own words, and copying information from public sources. As it states in Title 17, Section 103, "The copyright in a compilation or derivative work extends only to the material contributed by the author of such work, as distinguished from the preexisting material employed in the work, and does not imply any exclusive right in the preexisting material. The copyright in such work is independent of, and does not affect or enlarge the scope, duration, ownership, or subsistence of, any copyright protection in the preexisting material."
Whether or not a work is subject to copyright protection could be the subject of a lawsuit. For attorneys, copyright law is only part of a larger law practice that might include trademarks, tradenames and other topics and is known as intellectual property law. To avoid a claim or controversy, it is a good idea to obtain written permission to use any work that might be subject to a copyright claim.
Here are some good sources for information on copyright:
U.S. Copyright Office
Stanford University Libraries Copyright and Fair Use
University of Texas Copyright Crash Course
ninch Issue Resources