So how does that explain I can take 10 100ml bottles and an empty 1l bottle through security but not 1 full 1l bottle?
Good ole step functions.
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.
Charge a fee based on the number of ppm's your car emits:
tax * ppm = fee to renew your tags
tax * ppm * miles driven last year = fee to renew your tags1 US liquid quart is about 946.353 milliliters.
Why not just say 1 litre and have the same limit as the rest of the world.