Is it legal to install used catalytic converters on a car that previously had them removed?

The legality of installing used catalytic converters varies by jurisdiction. In many places, it is illegal to install a used catalytic converter that is not compliant with emissions regulations or not the same type that was originally installed on the vehicle. Additionally, some regions require that catalytic converters be new or refurbished to meet specific standards. It's essential to check local laws and regulations to ensure compliance.