Barry, the problem here is that the cops themselves are not engineers. So they can't differentiate the difference between engineered items and non-engineered items.
If they see an item which is 'non-standard' or 'does not comply with code xxxx' its is up to their discretion to defect you or not.
That yellow sticker doesn't actually mean your car is defected. It just means that the cop THINKS that your car is defectable and you are to prove them otherwise by clearing that defect.
Now this is where the controversy lies. Say your car is fully engineered. You have spent time and money getting your car to a safe, acceptable and legal level.
A cop comes along who had a bad day and gives you an EPA. You have to now waste YOUR time and YOUR money proving that your car is indeed roadworthy and legal.
So if you do pass the test, why the FFFFUK should you have to pay it? You knew, and so did the engineer who tested your vehicle, that your car would pass the test.
If there was a system where you can get a refund after PROVING that your car is indeed roadworthy and legal that would be fair.
But at the current state of things, its plain daylight robbery.