Comment by krisoft

I don't get your point about the tailpipe emissions. Of course there is a hard cutoff. What else could there be? Do you want them to gently suggest that you should maybe fix your car above 90ppm, and then rudely suggest from 95ppm?

The response they can do is that they either let you use the car or not let you use the car. That is binary. Technically they cannot even do that. All they can do is promise you that if you use your non-compliant car and they find it out they will fine you. Laws are after all just formalised threats backed by force.