I find this discussion intriguing. The German law cited earlier also forbids you from changing data (original German word "verändert" --- did I get that right?)
It seems to me this could make subject tagging illegal. In fact, a rigid interpretation could make SMTP illegal since you add a Received: header at each hop, and that's certainly modifying the data being transmitted. I believe this is a case of non-technical legislators completely failing to forsee the logical consequences of their law. :) Regards, David.
