I did some really hard digging and was about to give up but I found something that's close. It doesn't directly address the issue of copyright but might be a useful lead and help explain the reasoning behind it. As you know, an IP address can be transitory. The copyright perspective I read took a similar approach to the data protection line. Sorry, I couldn't do any better than that.

http://blogscript.blogspot.com/2008/01/ip-addresses-are-personal-data-of...