This has been called the Schwarzenegger v. EMA (Electronic Merchant Association). It started in 2005 and has been ruled unconstitutional by the supreme court since then. An earlier hearing was on Nov 20, 2010 I believe.
Apparently violent games can trigger young children into committing violence. Numerous articles online say that the Schwarzenegger side had several proofs linking violent games and youth violence. The only problem is several of the proofs have no citations and have been considered not credible.
IMO, when they used POSTAL and Counter-Strike as source of violence ,especially during the Virginia Tech incident, has dumbstruck me. In the end, video games was still ruled out as a source of violence upon investigation by the police.
The music industry is also chipping in to the cause of EMA as they believe that if the bill was passed, it could bleed out into the music industry and be abused. "Violent music is the source of youth violence".....something feels rather similar here.