The Martin factory was experimenting with water based lacquer in light of the possible environmental regulations, and possible ending of NCL lacquer (never happened). The environmental regulations were tightened up, but not to the extent that NCL was completely prohibited. NCL is still being produced, but much harder to get. I understand it is harder to get in the US than in Canada, but even in Canada, it takes some effort.
I keep seeing it in rattle-can units from places like Stew-Mac, but suspect maybe it's the industrial-strength/quantity put-ups that are harder to find, likely due to makers dropping out of the market?
And maybe that due to reduced overall demand?
Auto makers got away from it over 20 years ago, it started going acrylic (water-based) in CA
in the '70's.
I do recall somebody mentioning that inter-state shipping of the rattle cans could be problematic but thought it was due to the flammable-substance-in-pressurized-can issue as opposed to potential pollutants needing CARB "permits".
One can still go to a hardware store and buy sprayable NCL lacquer paint here, so suspect CARB was primarily focused on industrial-sized polluters and has a different set of rules for "hobby" end-users.
And I have seen descriptions of water-base lacquers as well, but last time I looked the descriptions got vague about whether they were really
NC lacquers.
Only said they were "comparable".
AFAIK genuine NCL is still the only one that constantly gets lighter/thinner by off-gassing and is re-soluble in new NCL, allowing great ease of touch-up or larger finish repairs.