I was told twice not to have gas in my metal jerry cans in the NF here in Kali. I think it was a 300 or 500 dollar fine per can with fuel. I tried to verify, but like lots of laws here, I could not find a code or ordinance stating this. The best I could find was a ca dot rule about the nozzle and the can being able to "permeate", probably similar to the cow fart code.
That is odd.
Here is a USFS webpage showing a Blitz metal jerry can with CARB spout as approved for use by the Forest Service itself, supplying the California address for McMaster-Carr as an approved source.
https://www.fs.fed.us/t-d/fueltran/sources/gascans/carbjerr/index.htm
I think someone misinformed you.