But who knows. I'd want to talk to a divorce lawyer or judge.
I just wanted to clarify the common misconception that you can "marry someone and take half of their [existing] stuff".
Again I think this varies from state to state but at least in CA considerations like this make zero difference. You split anything acquired during the marriage 50/50. Period. I imagine the intent of this rule is to limit the legal wiggle room and consequently the court costs of a divorce but the first thing they'll tell you is to not even use the word "fair".
But you're right that things you owned beforehand remain yours.
And on top of that the judge that ultimately reviews the case can change the terms even if both parties have agreed to them. Presumably this is to fix the problem of making someone sign to a unfair arrangement under duress.
This annoyed me (scared me, really) when I went through my divorce, but ultimately our agreement went through the court unscathed (pretty much just 50/50, though certain things are complicated, like how do you value the dog??).