Disclaimer: I am far from being a lawyer or even a constitutional scholar. I am just an American citizen with funcitoning intelligence and some decent background reading. What follows has not been supported by the Supreme Court (more's the pity) or any other competent legal body. If you find me unconvincing, perhaps you'd more enjoy the much more extensive amicus brief filed by 46 law professors on 2001 January 26 in the DeCSS case. By the way, many thanks to the obnoxious Anonymous Coward on slashdot who inspired in me the effort to clarify and codify my opposition to the DMCA on constitutional grounds.

Article I, Section 8 of the Constitution of the United States of America:

[Congress shall have the 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]

Fact: The DMCA makes it illegal to reverse-engineer or otherwise circumvent any "acces control mechanism", even when such circumvention is intended to exercise Fair Use rights.

Fact: The DMCA does not specify, grant, or recognize any time limitation on the validity of the access-control mechanisms. That is, there is no given time after which it becomes legal to circumvent the mechanism.

Fact: For now, at least, copyright does expire (if only in 120 years or whatever) and hence, works will pass into public domain. In fact, DMCA could be used to protect works copyrighted long ago as long as the mechanism is true. Therefore, at some point (perhaps soon), public domain works will be locked behind proprietary access-control mechanisms.

Implication: By wrapping content in access-control mechanisms, a content provider can charge access fees and so control the distribution, even of a public domain work, essentially forever.

Fact: "Forever" cannot be properly encompassed within the term "limited Times".

Conclusion: The DMCA is unconstitutional.

Valid? Through some crime of happenstance, I don't happen to sit on the Supreme Court, so I can't say so definitively. Is there enough there as to question the constitutionality of the DMCA? You bet.