What starts in California contaminates the rest of the country.
No, it doesn't. Been hearing that for years.
It does. Take some firearm models that used to be better no longer available due to the CA market. The Ruger MKII for example was much better than the MKIII, but because of CA they created a single model they could sell to the entire market.
The same can be said for other firearm models that have a smaller market because they cannot be sold in CA, and similar states. If other states follow suite you end up with various small markets, which increases the cost of firearms because they cannot be massed produced the same way for a single giant market, unless they are a type that follows the laws of the entire market.
Assault weapon bans started up in places like CA. CA senators were then key in drafting them for the entire nation a short time after. That was almost permanent, and only went away because it had a sunset provision.
The same will go for cartridge tagging etc If a big segment of the market requires a firearm that partialy ruin and imbed a number in ejected brass, many models without that will fade away. Some cities and PDs in states without it might require it to better track officer involved shootings or some other imagined benefit, and the plague spreads.
Eventualy politicians are citing it as a good idea in other parts of the nation.
If such technology results in a need to restrict the parts of a firearm that are involved in the markings created, a free market in barrels, ejectors, slides etc could shrink. Things like aftermarket barrels, and conversion barrels with already a small market could have such a reduced market they disappear.
Many smaller gun makers that cannot afford to retool simply make less profit, have a smaller market, or disappear.
So you have less overall variety, and at higher prices even in a free state. Plus national level restrictions inspired from state ones.
So even when something only stays law in CA it effects others. However it often inspires other politicians elsewhere to try to infringe in similar ways. It sets a precedent of infringement.