What Barrett is doing is great, but as far as for not selling to any government agency in California, it isn't like Barrett has a lot of government contracts there. The big money is with the military contracts and the US military in California will get all the Barretts they want.
It isn't the same thing as when Glock, Sig, Beretta, or S&W gets a contract from a large department for 5,000, 10,000, or 20,000 guns. LAPD might have, what, 2 or 3 Barretts?
So what will all those California agencies do to get Barretts? Simple, they will pay a little more and order them through a 3rd party vendor. They can get all the parts they want the same way.
I understand the sentiment that Barrett is sticking it to California, but keep in mind that the people that might be most hurt by his political efforts won't be the politicians who came up with the stupid notions of banning the guns, but the officers who would be deployed with the Barretts and the officers they support. The people Barrett is sticking it to are not the ones who need and use the guns.