At this point it's hardly the law and the constitution. These are just unpredictable whims of the people in power.

Not really a matter of forgetting. Trump was a leading advocate for Brexit. He wants to see the EU dissolved.

To do so legally, Constitutional Convention. 2/3 of states would have to agree to let it go. And everyone would have to hammer out what happens to federal assets inside the state.

At the moment, California is taking signatures for studying a "CALexit" plan. It is about 500,000 signatures by July for a successful petition. After that, California starts to study the costs, opportunities, logistics, and other aspects of leaving the union.

There is basically zero chance they successfully secede. There is however a slightly above zero chance they seriously try.

California trying to secede would be stupid enough to make Trump look like a top mensa candidate.

the same thing for texas to become it's own country, that said, it's not happening.