Start with the recorded deed to see whose names are listed and how ownership is held. California's general community-property rule may also matter: state law generally treats property acquired during marriage while a spouse is domiciled in California as community property, subject to exceptions.
That general rule does not answer who can sign for a particular house. How the property was acquired, the deed, a divorce judgment or agreement, and any court order about the house can affect the sale. The title company reviews the documents and confirms the signatures and closing requirements; a California family-law attorney can explain what an agreement or order means for your situation. You can talk with us while that review is happening.