If your case has been sealed/expunged, you will not have to disclose the matter.  Arrests are usually not considered bad acts, per se (think evidentiary law) but you should review the guidance for California Bar requirements.  If it helps, consider discussing the matter with a criminal defense attorney, because while expungement laws differ from state to state and full faith and credit clause may work in the courtroom, it may not be necessarily applicable to your application. It never pays to lie, so you need to ensure that what you are disclosing is truthful.  If the question asks for arrests, and your arrests were not expunged, then you may need to disclose and discuss.