As at September 2014, the California DMV website says that you need a smog certificate from a STAR station if your DMV registration renewal notice states your vehicle requires a smog check. This system replaced the Gold Shield and Test Only program in January 2013.
Smog inspections are required unless your vehicle is a hybrid, an electric-powered vehicle, a motorcycle or a trailer. Owners of gasoline-powered 1975-year model vehicles or older and diesel-powered 1997-year model vehicles or older also don't need to obtain a smog inspection. There are very specific rules regarding smog certificates which should be checked through the California DMV.