Due to high levels of SMOG and other toxins found in LA's air and surroundings, Cali has one of the stringest inpsection standards. This is why they do not want you to modify your car in any way or form that will or I should really say "may" make the problem any worse.
A CARB sticker which stands for California Air Resources Board, states that the modification and or part you're installing has been tested and will not increase and or modify the vehicles emissions levels. To people living in Cali this is VERY important, becouse if you are caught in a "tuned up" car, the cops can and will often ask for you to pop open your hood, where they will be begin to look for aftermarket parts and the corosponding CARB sticker. If you do not have the right CARB stickers, you'll be issued a slue of tickets.
In NY you don't have to worry about CARB stickers. Modifications such as intakes, and whatnot will not effect your emissions to such a point where you wont pass a NY state inspestion. The standards for emissions are strict here as well, but not as strict as those in Cali.