SohoRedondo: Yes, definitely. It is a Code and it is not only strictly enforced by local Building Inspectors but also by Buyer's Inspectors during the future sale of your house.
We are very frequently called back after final inspection and asked by HomeOwners to remove air gap so they can install lotion dispenser, or other fixture, in its place. For some reason, most people are anti-air-gappers
However, we are also called back with same frequency during the sale of the house to re-install air gap when Buyer's Inspector includes "No Air Gap / Code Violation " in his/her inspection report.
That little "ugly $7.00 thing" called "Air Gap" is now holding your one million dollar house hostage. Or as Redondo Beach area goes - two million dollar house.......