My understanding is that such parts are not by themselves illegal. The crime is actually using them on the road. My understanding was that they were legal for track purposes.
I would never want to say that people should be able to defeat emissions, but a part of me does not like the idea that every vehicle owner is beholden to the OEM for parts in perpetuity. The "right to repair" people should be all over this fight. Restrict cars to only their original emissions parts and that becomes yet another lever for manufacturers to pull when they want to sell new cars/trucks/tractors. I say let people use the parts they want to use, then properly inspect and test the resulting vehicles once they are on the road.
I would never want to say that people should be able to defeat emissions, but a part of me does not like the idea that every vehicle owner is beholden to the OEM for parts in perpetuity. The "right to repair" people should be all over this fight. Restrict cars to only their original emissions parts and that becomes yet another lever for manufacturers to pull when they want to sell new cars/trucks/tractors. I say let people use the parts they want to use, then properly inspect and test the resulting vehicles once they are on the road.