Steve: I may not actually be a lawyer yet, but I do know that if he is using the band's trademarked logo without their consent in a transaction purely for his own financial betterment (i.e. using someone elses name to make a profit), he is leaving himself wide open for copyright theft and possibly obtaining by deception if people are buying it thinking it is official band merchandise.
I'm sure that Dark Tranquillity as band may see the funny sign of this, and the seller isn't stating that they are official, but neither is he stating they are 100% unofficial. If I were him, I would take them off ebay until he contacts the band and obtains consent from them to continue.