Legal Question in Family Law in California

They can file that way, but if they continue to cohabitate a judgment of legal separation will probably not be granted, or would be voidable.

2310. Dissolution of the marriage or legal separation of the

parties may be based on either of the following grounds, which shall

be pleaded generally:

(a) Irreconcilable differences, which have caused the irremediable

breakdown of the marriage.

(b) Incurable insanity.

You can't really claim 2310(a) applies if you are still living together as a couple.

You could file, but how are you going to determine the date of separation when you are still living together. An arbitrarily picked number? Scissors cut paper?