Situation: you are licensed to carry a concealed pistol. You live inside an eruv. You choose to carry your pistol on shabbat.
What is the status of the Concealed Pistol License (CPL) ID card? Can we say that the CPL ID is "supporting" the pistol, and therefore it is not muksah and can be carried also? Or do we say that the CPL ID is not needed, because we can prove to the police that we are licensed after the fact?
Aside: I'm thinking of getting a scan of my CPL printed on to a t-shirt...