California requires galvanized pipe for outside while black can be used indoors, and New Mexico seems to require black pipe.
When the gas company ran a line to my NM house in 1974, they used black pipe covered with a tar-asphalt and a paper outer coating.
Wisconsin Energy Co. uses nothing but black iron from the meter (outside) to the appliances inside. From the pressure reducing valve at the meter to the main (tared and paper wrapped welded steel pipe, buried about eight feet down along side the rural road) they run a plastic semi flexible pipe. The joints are made with an electric heater which heats the plastic pipe to the point of softening after which the joints are more or less swagged together. The resulting pipe is pressurized with compressed air to 100 psi and all joints are bubble tested with a soap solution. The pipe is left for about an hour while monitoring the pressure, if it remains constant at 100 psi the pipe is vented and then the tap into the main is opened. I've seen that yellow semi flex pipe used all over on new construction and retrofitting old.
Regards,
GtG