The Department of Land Transport (the Defendant No.1) issued the Ministerial Regulation on a Taxi Carrying Passengers Not More Than Seven Persons Registered in Bangkok, B.E. 2550 (2007). The Clause 10 of the Regulation requires a public taxi carrying not more than seven passengers which was registered since 2nd January 2009 to only use natural gas for vehicle (NGV) in combination with gasoline but not liquefied petroleum gas (LPG). Passenger Vehicle Operators (the Plaintiff No.1) and Association and Taxi Isara Cooperative Limited (the Plaintiff No.2) were not able to register new taxis to replace their old taxis due to the Regulation so they filed a case with the Administrative Court to set aside the Clause 10 of the Regulation.