It seems the ruling of the 5th circuit court of appeals would be relevant here... ? They said that DCMA couldn't be used to prosecute someone for bypassing encryption for the purposes of using or viewing something when doing so was not itself a breach of copyright.
I'm probably hacking the words up, but there are some quotes from the judge here:
http://www.courthousenews.com/2010/07/23/29099.htm
"Merely bypassing a technological protection that restricts a user from viewing or using a work is insufficient to trigger the (Digital Millennium Copyright Act's) anti-circumvention provision,"
"The DMCA prohibits only forms of access that would violate or impinge on the protections that the Copyright Act otherwise affords copyright owners."
"The owner's technological measure must protect the copyrighted material against an infringement of a right that the Copyright Act protects, not from mere use or viewing."*
That remains standing as the last word from the US courts, AFAIK.