"In no case does copyright protection for an original work of authorship extend to any idea, procedure, process, system, method of operation, concept, principle, or discovery,
… regardless of the form in which it is described, explained, illustrated, or embodied in such work." 17 USC § 102(b). "Copyright protection under this title is not available for any work of the United States Government [i.e., works created by federal employees]." 17 USC § 105. Once copyright expires a work cannot be copyrighted again. Published works that failed the necessary formalities in force prior to 1977 never had any copyright and cannot be copyrighted. (MORE) 
