Emission laws are FEDERAL. It's enforced locally (which depends on where you live).
Besides the possible $10k fine...you can also get fined if you SELL the vehicle to someone without the cats.
Obviously it's NOT enforced as stringently as it should. Some states (like NY and MA...) if a mechanic notices the emissions have been tampered with..they are REQUIRED to NOT allow you to drive your vehicle and call the police to impound your car.
Besides the possible $10k fine...you can also get fined if you SELL the vehicle to someone without the cats.
Obviously it's NOT enforced as stringently as it should. Some states (like NY and MA...) if a mechanic notices the emissions have been tampered with..they are REQUIRED to NOT allow you to drive your vehicle and call the police to impound your car.