Haven't there been major scandals in the appraisal and verification, as well as art still being stolen and successfully sold in black markets?

I'm hoping a law helps, but I won't hold my breath.

What helps with art is people with art want to show it off. Steal some art and you risk showing it off to someone who knows who it belongs to.

Is this really the case? Isn't a great deal of stolen art not shown around so it can't be identified? I wonder if most stolen art is kept in vaults and never shown to anyone.

Some is, but most people who steel art want to look at it.