The issue of loss of copyright when a work passes into the public domain is not the same as Fair Use. One of the reasons that large corporations, like Coca Cola, defend the use of their Trademarks and copyright is to prevent their products from becoming so commonly used as to pass into the public domain. Unfortunately for the individual using others' works, there are no clearly delineated guidelines as to what constitutes fair use or when an otherwise protected work passes into the public domain.
The only way I can determine the limits of copying is to look at what the Courts have decided is or is not fair use. Similarly, the only way to tell of some work has passed into the public domain is to resort to court decisions. That is the bad news and there is no good news. There are an extremely limited number of copyright cases concerning genealogy so there isn't much direct guidance. But there is a lot of indirect guidance in the form of similar issues decided by the courts. Remember, that all copyright cases have original and exclusive jurisdiction in the Federal Court system. You cannot go down to your local Justice Court or Municipal Court and file a copyright claim.
So how do you prove a copyright case in court? One of the most common standards applied by the courts reads like this:
If is beginning to sound impossible with terms like "substantially similar" you need to understand that lawyers deal with that kind of stuff everyday. In that same case, Hogan v. DC Comics, 983 F. Supp. 82 (N.D.N.Y. 1997) the Court explained why it held a copyright violation by saying:Plaintiff may prove defendant's copying of copyrighted work by showing: (1) that defendant had access to plaintiff's copyrighted work, and (2) that defendant's work is substantially similar to plaintiff's copyrighted material. See Hogan v. DC Comics, 983 F. Supp. 82 (N.D.N.Y. 1997)
As other courts have noted, the determination of the extent of similarity that will constitute a substantial similarity—and hence an infringing similarity—presents one of the most difficult questions in copyright law. See Warner Bros., Inc., v. American Broadcasting Companies, Inc., 654 F.2d 204 (2d Cir.1981). “Somewhere between the one extreme of no similarity and other of complete and literal similarity lies the line marking off the boundaries of ‘substantial similarity.’ ” 3 Nimmer on Copyright § 13.03[A]. As Judge Learned Hand has remarked, this line “wherever it is drawn will seem arbitrary.” Nichols v. Universal Pictures Co., 45 F.2d 119, 122 (2d Cir.1930).Hogan v. DC Comics, 983 F. Supp. 82, 86 (N.D.N.Y. 1997)
So then, what do the courts say about Fair Use? As you can imagine, there are a huge number of cases on Fair Use although, as noted, very few refer directly to genealogy. First of all, the courts acknowledge that the whole issue is vague. In the case of Campbell v. Acuff-Rose Music, Inc., 510 U.S. 569, 114 S. Ct. 1164, 127 L. Ed. 2d 500 (1994), the court essentially held that Section of 1976 Copyright Act describing fair use doctrine requires a case-by-case analysis and not rigid application of bright line rules; statutory examples of permissible uses provide only general guidance.
What is clear is that copying an entire work is protected. What is not clear is how much of the work can be copied before the copyright holder has a claim in the courts. As a matter of interest, the Federal Regulations prescribe a specific form of notice for copying materials from libraries and archives. Here is the wording of the notice:
That helps a lot doesn't it?