In all states, you do have a right to defend yourself from physical harm or death. You can use the appropriate level of force that is necessary. It could include everything all the way up to deadly force in a case where you genuinely fear for your life or the life of someone else, such as when someone has broken into your house with a firearm.
That being said, there are some states that have a duty to retreat if you are not inside your house. For instance, maybe the altercation took place in a parking lot or on a sidewalk. Individuals are expected to try to avoid the confrontation if they can and to only use force if they know that they have no other options. Does California have this law?
There is no duty to retreat
In short, no, you are not required to retreat in California, and you can certainly stand your ground and protect yourself. This does not mean that you can be the aggressor, of course, but you also do not have to flee before that aggressor instead of using physical force as a means of defense.
This is especially true in your house because you can use the Castle Doctrine. You are allowed to defend your home and your family if someone forces their way inside and you believe you’re in danger. But since California does not have a duty to retreat, you are typically free to stand your ground in any location. You just need a legal right to be there.
That doesn’t mean you won’t face arrest after the altercation, however, so make sure that you are well aware of all of your legal defense options.