the increasing challenge of copyright

The current D-Lib Magazine contains an interesting article, written by Peter Hirtle (the Intellectual Property Officer at Cornell University), that describes the difficult issues involved with works previously thought of as falling into the public domain. His argument is complex, but in summary: because of international agreements that the US government has entered into,

it is almost impossible to determine with certainty whether a work published from 1923 through 1963 in the US is in the public domain because of copyright restoration of foreign works.

Hirtle reviews two titles, both of which were published in 1940 by the same company; both items contained a notice of copyright, but neither of work's copyrights were renewed with the Library of Congress. One, he asserts, is still under copyright protection while the second is in the public domain. To determine this through investigation for the works in question ("published from 1923 through 1963 in the US") is, as Hirtle argues through the examples, either difficult or impossible.

If anything, Hirtle's analysis provides another example of the intellectual property challenges in building digital libraries.