It is one thing to regulate emissions. Telling anyone what they must use to achieve emissions is wrong. An open market is able to find equivalent alternatives. This creates an innovative industry. It also makes competition for the auto industry that for components suppliers in check. The only reason to regulate emissions based on equipment is to create a monopoly controlled by the manufacturers. This is why your catalytic converter gets stolen and costs a fortune. It is a monopoly without open competition. It is the most corrupt form of capitalism: closed market. This is what killed car culture and the grassroots engineering that it supported. This is why there were no new grassroots innovative automakers in since the 1970's. The people that are actually interested in cars and tinkering have been legislated out of existence. Telling people what they must use for parts is theft of ownership and irresponsible nonsense. The responsible option is to regulate emissions based on test results. Imagine if the speed limit of the road was hard wired into your car. That would be the same thing as regulating emissions based on equipment. You are too incompetent to drive the speed limit and so your car always goes the speed limit regardless of conditions. Ownership is so eroded and warped in the USA people are too stupid to know that this is the real freedom the country was founded on. Ownership is everything.