Possessing a nobleman's amulet doesn't make you a nobleman. It means you found it, stone it, took it from a nobleman's corpse, etc. I don't see how it can be construed as traitorous. Same for PD great unless you are in the PD. People (especially adventurers) find stuff all the time. Unless we make it possible for people to turn in these items for reward?
I'll do a little research this weekend for FR contraband items.