Eldred v. Ashcroft
537 U.S. 186 (2003) - full text opinion
"Actually, Sonny wanted the term of copyright protection to last forever. I am informed by staff that such a change would violate the Constitution. I invite all of you to work with me to strengthen our copyright laws in all of the ways available to us. As you know, there is also Jack Valenti’s proposal for term to last forever less one day."
Eric Eldred, along with some other plaintiffs, saw the law as effectively violating the Constitution's restriction, in Article I, Section 8, Clause 8, that copyrights only last for limited terms. Congress has repeatedly passed laws extending copyright protection; each time diminishing the amount of works available to the public domain.
Although the CTEA was upheld, many of the plaintiffs and lawyers in this case, including Lawrence Lessig, have set up Creative Commons, a foundation dedicated to creating a smaller and more flexible copyright regime. If you have a work that qualifies for copyright protection, you can choose from a wide variety of licenses.