While I agree with telling Trump to go lick Elon's balls, states are specifically forbidden from entering into trade agreements with foreign countries by the Constitution. To do this, California would need to be willing to secede from the Union. I'm okay with it.
And it's the same for the European union. European states can't get trade agreements by themselves. So when you read "Italy is ready to talk with trump" is just sucking dick
The best I could tell from the article was that all he was doing was essentially lobbying foriegn countries to tailor their responses so that they hurt california less than other states. I can't see any law blocking that. From what I could tell he wasn't even offering anything real in exchange.
Texas couldn't secede, probably because it's a red state..how amazing would it be if California became it's own country with actual progressive laws. I for one would allow it. Let them become Canada, Mexico or even it's own. Do it Cali!