I am not a lawyer. This my opinion, not legal advice.
On this question, I believe the two questions would be separate, but, I also believe it would depend on jurisdiction of the incident. Would likely be handled differently in Austin vs Tyler, for example.
A legally justifiable defensive gun use is still legally justifiable, even if the person defending was in a place that prohibited guns. The defender could still be prosecuted to the extent that 30.05/06 provides for prosecution of violators.
Again, my opinion only.