Once you are convicted of domestic violence, you are prohibited from owning or possessing a firearm in California. Assembly Bill 3129 amended Penal Code 29805, and makes it illegal for anyone who was convicted of misdemeanor domestic violence for having possession of a firearm.
Also under California law, the court can prohibit you from possessing or purchasing a firearm even in a situation where you have only been charged with a domestic violence crime, but not convicted.
Under federal laws, you are prohibited from possession or owning a firearm regardless if it was a misdemeanor or felony domestic violence case.
Additionally, If the judge imposed specific court orders, you will be prohibited from possessing, buying, purchasing or receiving ammunition while the order remains in effect:
- Civil harassment restraining order
- Domestic violence restraining or protective order
- Workplace or private school restraining order
- Protective order for elderly
- Emergency protective order related to stalking
It's also possible for anyone can seek a domestic violence protective order that would prohibit buying or possessing a firearm if the victim was a spouse, ex-spouse, cohabitant, or family member.
However, If the case was fully dismissed, following the diversion, then yes you can own firearms. Under the federal law on this subject, a dismissed case (even after a deferred sentence or diversion) is not considrered a conviction for the purpose of firearm preclusion.