Catalytic converters being targeted by thieves

Catalytic converters being targeted by thieves - MOUNT VERNON -- Local law enforcement reported at least five incidents in the past week of people claiming their catalytic converters were stolen. [Mount Vernon News]
How hard is this to curb? Require scrap metal dealers to take a digital photo or require photo id with an explanation of where the converter came from.  This isn't to much to ask from them.
I go to scrap yards all the time and they are full of undersireables toting in goods that I would bet are stolen. They get enough to have a few beers or a crack fix. They're not hard to spot. Of course, good people go there too, but the stuff they're bringing is obviously from projects and what not.