That article reads like a sub plot out of Breaking Bad. Makes sense though. Once pulverized into basically raw material, it is almost impossible to track and easy to handle/transport. There are plenty of metal refiners that could care less where it came from, as long as they are not breaking any...
I've wondered the same thing. On the surface, you think it would be easy. Just outright ban the recycling of any catalytic converter, unless you give a driver's license, proof of address, and documentation (title, bill of sale, registration) that you own the vehicle.
But I think what happens...
Sad sign of the times when even Slee is making cat guards not to protect against errant rocks but instead tweakers with battery powered sawzalls. Never saw this coming.