Yes you have to be 17 to pre-order games. The game industry is self regulated meaning retailers aren't supposed to sell M rated games to children that are under that age of 17. That is just how it goes. The law in California had nothing to do with the ESRB and actually wanted to overrule it and make it a crime to sell games to people under the age of 18.
The law was unconstitutional because it broke First Admendment laws, this just simply means the government can't control the distribution of video games in that manner. It doesn't change the way the ESRB operates or the self regulation inside the video industry
Is it illegal to sell or rent M (Mature) or AO (Adults Only) rated games to children under 17 and 18 years of age respectively?
ESRB supports retailers? voluntary policies restricting the sale or rental of M (Mature) and AO (Adults Only) computer and video games in the United States and Canada to customers 17 and 18 years of age or older respectively unless permission from a parent has been obtained. Through efforts such as the ESRB Retail Council (ERC) and a strong commitment on the part of major video game retailers, stores have vastly improved the rate at which they comply with these store policies, as measured by both the ERC mystery shopper audits as well as those conducted by the FTC. More information on federal, state and local regulations in the U.S. is available through the websites of the Entertainment Merchants Association (EMA) and Entertainment Software Association (ESA). In Canada, you may contact the Entertainment Software Association of Canada (ESA Canada) or the Retail Council of Canada (RCC).
Source: http://www.esrb.org/ratings/faq.jsp#24
So you may find a retailer that will sell you a game, you may not. It is up to them.
EDIT: No I did not agree with the new regulation proposal. It was basically saying to parents that they don't know how to raise their children properly. The government needs to figure out something else to attack instead of video games. Video games don't make people crazy, genetics and poor upbringings do. Try fixing the latter but increasing social programming and mental health programs.
