How would you implement this? How does a police officer know which car is an offending VW or not? Where does it end? Vehicles that were build prior to tougher

How would you implement this? How does a police officer know which car is an offending VW or not? Where does it end? Vehicles that were build prior to tougher emission standards? What about gas engines that are just inefficient, like lawn mowers? The police just don't have the resources to make these type of nuances decisions. Note: I own a 2016 VW Golf R, and a 2003 Golf GTI.