Gov. Gavin Newsom announced Sunday that he signed legislation to crack down on rampant vehicle catalytic converter theft by making it illegal for recyclers to buy the valuable car part from anyone other than the legal owner or a licensed dealer.

The anti-pollution devices in cars contain valuable metals such as rhodium, platinum and palladium. The often untraceable parts are easy to saw off from a vehicle, making them an attractive target for those hoping to make a quick buck at a scrap yard.

The two new laws will increase penalties for buyers who fail to certify that a catalytic converter wasn’t stolen, which is expected to make it more difficult for thieves to find a marketplace for the parts.