To issue a declaratory judgment in this case, the court would have to find that Merriam-Webster has no claim of copyright infringement over any portion of the material Richards proposes to use. Richards does not make such a claim, nor does he allege that Merriam-Webster's copyright certificate is invalid. Accordingly, his claim that some entries may have entered the public domain is an insufficient ground for a declaratory judgment of noninfringement of the work as a whole.
Source: wiktionary