Adding chemicals to gasoline is far easier than embossing individual stampings into steel. The law calls for individualized marks that are on the chamber as well as the firing pin. So after one barrel is made, the yet-to-be-invented tooling must change before the next barrel is made. Doing this on an outer surface is easy, but on an inside surface? Guess again. It’s an expensive proposition and the CA market just isn’t worth it; especially if being seen as bending to the will of Kamala Harris hurts a gun maker’s sales in the rest of Free America. (Think of Smith and Wesson’s former British owners kowtowing to the Clinton Administration.)
I missed that part in the story. You are suggesting it's not economically or technologically feasible. I disagree, CA is a very large market, even with their crappy laws. There will be gun manufacturers willing to go through the expense and add the price to the weapon, even if it's sold in AZ. It hasn't been invented yet because there hasn't been a demand. There will be if CA gets this law. I can easily imagine a device using a laser and tiny mirror that could engrave something into the inside of the breech end of the barrel. It, too, would be easy to defeat with a pencil and fine-grit emery cloth.