In its answer and counterclaims against Blizzard Games and Vivendi Universal Games, Bnetd claims that the DMCA is unconstitutional, and that Bnetd developers did not violate the statute when they created its multi-player gaming server.
Fourteenth Affirmative Defense (from the counterclaims):
Defendants actions are lawful because Title 17, Section 1201(a) is unconstitutional on its face and as applied under the First Amendment and/or the Copyright Clause of the United States Constitution and because passing Section 1201(a) is not a valid exercise of Congress' enumerated powers.
More documents are here. Ernest Miller's past coverage of the Bnetd case is here and here.