ApexProcyon: I think that it should be judged in the same way as assisting someone in suicide with disturbing the peace of the grave as secondary crime.
But surely the motivation must count for something...if you assist someone in committing suicide because that person is incurably sick, and you don't gain from that person's death in any way, that might possibly be even seen as an altruistic deed. Cannibalism, even if the "victim" wants it, is different imo.
But it's a very hard question imo. There actually was another such case in Germany recently, with a former policeman who fantasized about cutting up a corpse meeting a guy on the net who fantasized about being butchered...well, ended with the latter dead. The case went up to the highest court after multiple appeals and the former policeman was eventually sentenced to life in prison (which means at least 15 years in Germany) for murder. Very odd case, and I do think some punishment was justified, just not sure if that wasn't excessive.