DALVEER BHANDARI, J.

( 1 ) LEAVE granted.

( 2 ) THE appellant Bharat Petroleum Corporation limited has filed this appeal against the judgment of the high Court of Delhi passed in writ petition No. 5532 of 2007 dated 29th October, 2007.

( 3 ) IT is imperative to evaluate the historical perspective in order to properly appreciate main issue involved in this case. The notification no. GSR 686 (E) dated 20th october, 2004 is in issue by which sub-rule (14) was inserted in Rule 115 of the Central Motor Vehicles Rules, 1989. This sub-rule prescribed the mass emission standards (Bharat Stage-III which is popularly called euro-III)) for four wheeled vehicles. This notification was based on the judgment of this court in M. C. Mehta v. Union of India and Others (1998) 6 SCC 63. The relevant portion of the notification dated 20th October, 2004 reads as under:-

" (1) These rules may be called the Central motor Vehicles (Fourth Amendment) Rules, 2004. (2) They shall come into force- (a) in the National Capital Region and the cities of Mumbai, Kolkata, Chennai, bangalore, Hyderabad including secunderabad, Ahmedabad, Pune, Surat, kanpur and Agra in respect of four wheeled vehicles manufactured on