People bought diesel vehicles because of it's less cost of running and all these private diesel cars are used to commute from point A to point B. They have paid for these vehicles from their hard earned money keeping in mind that it can be used for 15yrs. When they bought these cars till 2015, before NGT's and Supreme Court ban on diesel cars, they had no idea that NGT and other higher authorities will enforce their ruling on common man. 

This is a petition to Indian Government to allow private diesel vehicles to be used in Delhi/NCR as per vehicle's existing validity on it's registration certificate because when people bought these vehicles they were not aware about any such ban on diesel vehicles. Now everyone is aware about new validity of diesel vehicles, so that gives them the visibility and clarity to decide if they want to buy a diesel vehicle or not - WHICH was not there before 2015.