Not brilliant, but what if ... Already are magic artefacts. For example swords could have "souls", and a spell by owner could pass over ownership to new owner by letting know the soul the change 
That would make theft of items impossible then. Please read my previous post

AFter pressing post I was informed another post had been made, looking at it its even more outrageous than the first

Long term bad luck?

Perhaps we should leave theiving possible?
Ohh and @ Izzy:
lol i can't believe they would do that, ohh well, serves them right I guess
