The practice of a man removing his condom without the woman knowing has been referred to as "stealthing".
California is the only state in the US to have such a specific law.
(12% of the US population lives in the state of California)
It's not incredibly surprising. California is considered one of the most "progressive" states. This same type of law also exists in Sweden, and played a major part of the story in the Julian Assange case, if anyone is familiar with that.
What this means is that a man will risk being charged with "sexual battery" if the woman he is sleeping with claims that he removed his condom without her knowing. To be on the safe side, the man will have to obtain her explicit verbal consent before removing the condom, if he is going to continue sexual intercourse with her.
The traditional conservative view, on the other hand, is basically that if a woman takes off all her clothes and lies in the same bed as a man, and has not said "no", then it should be assumed she is consenting to whatever sexual acts take place.