Got asked current salary, when I'm in CA and that is no longer legal. How can I report?

Exactly what the title says. I was asked my current base salary, not what I'm looking for. And when I refused they tried to pressure me into answering. I don't want them doing this to other people who don't know it's illegal.

I did try googling but didn't see any answers aside from "sue them". Shouldn't there be a way to report it to the labor board or something?