Eric Goldman (blog.ericgoldman.org) did a number of roundup pieces around first amendment defenses against prosecution under the CAN-SPAM laws, and the one of the arguments set forth by the MPAA in its defense of the DMCA was that its commercial speech rights were violated by people who could use DECSS(sp?) to unencrypt their DVDs and just watch the video content without the commercials. I'll see if I can find the case id and post a link.