Pornokitsch

Question that surfaced in my brain soup: who owns the publication rights to a convention sketch?

Artists are essentially doing commissions for cash - but who owns the copyright? I've seen some incredible assortments of original comic book art collected by fans... so what happens if they scan them and put them on Lulu.com?

According to the Fine Art Trade Guild, there's no easy answer, and people should be clear about it up front:

"An issue which is often forgotten, but which is important, is copyright. In most cases, copyright rests with the artist, and can be sold by the artist, as an entirely separate commodity from the original artwork. However, when work is specifically commissioned, copyright normally rests with the person (or organisation) who has commissioned the work." - Fine Art Trade Guild

I can see how that would be a tetchy issue. ("Mr. Ben Templesmith, do you mind doing a squid for me? Great! Now, how would you feel about me potentially selling it someday?") 

It seems even more complicated when characters are involved. If you've got Ben Templesmith drawing - I dunno - Batman, then it seems like you've got two degrees of copyright at stake.

Anyone know the answers?

[Update: Helpful response from Tor's Irene Gallo, via Twitter: Ownership, even when commissioned, does not include reproduction rights unless explicitly contracted.]