Works of authorship originate in private, safely kept under common law protections. Once published, however, expressive works become data ferae naturae—wild and natural information. As such, expressive works roam and reproduce freely. They may get captured in fixed copies, caged in atoms or bits. But the public, once it has absorbed an expressive work, generally retains relatively cheap access to it—unless and until copyright intervenes.
Copyright law limits public access to expressive works, herding them off the commons and into private hands. The Copyright Act offers a sort of ranch to authors, giving them a place to birth, raise, and sell their expressive works safe from the deprivations of grasping strangers. Authors enjoy those special privileges against the public not as a natural right, but rather solely thanks to a policy authorized by the U.S. Constitution and implemented through the Copyright Act. [The figure below] illustrates the path that copyright, together with some of its legal next-of-kin, takes from its origins towards its goals.
Expressive works begin as toll goods, excludable but non-rivalrous in consumption. In other words, an author can at first keep others from consuming her expressions thanks merely to her common law tort, property, and contract rights. She can keep her works in private, under lock and key, releasing them only upon solemn promises of secrecy. Those with whom she shares her work can enjoy it without at all decreasing her enjoyment of the same work; she can sing her song or study her painting just as well if others listen to or gaze on their own copies. That marks her work, like other works of authorship, as non-rivalrous in consumption. It retains that characteristic if and when she publishes the work, but then loses its excludability. Unless she were to somehow form and enforce a contract with everyone who encounters her published work—an unlikely prospect—only through copyright law could she protect her work from unauthorized access. Copyright steers published works back into toll good territory, empowering authors to assess fees and impose other limits on those who would use their works.
The Copyright Act’s privileges, because they restrict non-authors from freely copying a copyrighted work, defy natural and common law rights. That statutory negation of erstwhile public goods, however, arguably serves the public good. Though copyright restricts access to existing works of authorship, it encourages new ones.
[NB: The above text comes from chapter 1, § A of my draft book, Intellectual Privilege: Copyright, Common Law, and the Common Good. I will soon upload a PDF of the entire chapter, including footnotes. I welcome your comments.]