U.S. Constitution, Article 1, Section 8, Clause 8

All copyright power derives from 27 words in Article 1, Section 6 of the U.S. Constitution:

The Congress shall have Power . . . To promote the Progress of Science and useful Arts, by securing for limited Times to Authors and Inventors the exclusive Right to their respective Writings and Discoveries; . . . (emphasis added).

It does not state:

The Congress shall have the Power . . . To further the capacity of authors and inventors to extract any and all value that exists in their creations, by securing for a time in excess of the lifetimes of these Authors and Inventors the exclusive right to their respective writings and discoveries; . . .