Not a lawyer here, but...
My understanding and reading of the CA law is that it is illegal to bring them into the state, or to cause them to be brought into the state (such as mail order). Or, of course, to sell or transfer them to another party within the state.
My reading of the law, and general sense of things, is that the state of CA would be only too happy to see the west end of your eastbound hi-caps, even though you own them legally. (pre-CA-ban, of course?)
The proviso would be that you are selling them in a jurisdiction where it is legal to posess, buy, and sell them.
If you intend to sell them in Reno, for instance, that should be fine. I am not sure, however, of your legal standing if you take them to Reno intending to sell them, and then if you don't sell them, trying to return across the CA border with them in your posession. To be on the safe side you would need to check with an attorney who is well-versed in CA gun law.
Some CA people have recreational activities that they pursue in Nevada. To avoid having to transport their gear (ski's, jet-skis, snowmobiles, boats, etc) they rent storage lockers in Nevada. I drove from Carson City to Reno, and I swear to God, I know where Saddam Hussein stowed the weapons of mass destruction because DAMN are there a ton of storage locker facilities there. I'm not aware of any provision of either CA or NV law that would prevent you from renting a Nevada storage locker in which to keep all your non-CA friendly recreational gear in. Ask that attorney to be sure, but I think you'd be just fine in doing so.
