Is there any solution yet to preventing stolen cryptocurrency funds from being spent? Isn't the only solution to have a central database and require laws to require every transaction to be pre-checked to see if it's stolen funds or not?
And not only that, the centralized system will have to be constantly keeping track of wallet mixing to see where funds are being redirected to, attempted to being washed to?
Your example doesn't fit what I am saying either. With a digital currency you can do a pre-sale trick, so you'll see the funds were stolen - and you then don't sell them the car in the first place.
We can't incentivize theft.
It's a race against time. As soon as the coins are sent to a new address you can't know whether goods or services were exchanged in this process and you are thus punishing a well-intentioned seller as opposed to the thief.