Originally Posted by Scuba Steve33
Another example being military (if stationed in CA) if I understand this correctly?
If your Uncle issues those magazines to you, yes. If you then separate in CA and Uncle allows you to keep them, that's fine.
If you bought them yourself, for non-duty weapons, at some other duty station, and then came to CA, no. Similarly, if you separated outside of CA, cannot bring in the large-capacity mags you may have been issued.
Buying, for example, your own MagPul mags for your issued M4 hasn't been tested. I suspect, if kept with your duty gear and used only with your issued weapon, there would be no complaint.