I thought about even pushing the post reply button after writing this, but here it is.
There is nothing illegal about having a residence or place of business in a different state from where your DL is from and having a vehicle registered to that address in the other state. The government cant regulate that. It is also not illegal to bring an out of state vehicle to CA...doesn't matter who it is registered to. The "illegal" part is if any of it is untrue and not factual. But, what law enforcement agency is gonna take time to "prove" it? If you get stopped, say the wrong thing, go to court and change the story, etc, then you may have a problem.
You are a resident of one state at a time. Its OK to have a vehicle registered at your other states vacation home or business and then drive that vehicle here for a temporary visit or stay, or to work on it and you out for a test ride, or here for a special occasion. Doesn't matter where your drivers license is from. You also do not have to show insurance for an out of state registered vehicle in CA unless involved in a collision.
States also have the law to honor each other's laws. So, if a vehicle's equipment is legal in another state it is then legal here as well. Like if no turn signals are required in AZ then a vehicle registered in AZ is OK here as well. Another example is that CA requires a front and rear plate, but many states do not. You cant get legally cited for not having a front plate in that situation. Now you throw in Federal law which mandates manufacturers put on certain equipment stock. Like a KTM with the gas overflow canister that has a problem with filling up and stopping the bike if you leave it upside down for sometime. Its not legal to remove it by fed law. But for instance in CA there is no CARB testing for motorcycles. There are CARB rules, but no testing. So, if it gets removed few LEO are gonna know and all you can get is an equip cite. You just put it back on, get it signed off and back to it.
Now lets say I don't know the law as I stated about above. I do not know it all, but Ive been a cop for almost 30 yrs and was a motor cop enforcing the CA vehicle code for 15 yrs, CARB trained and tested, etc. So, I have no problem with my explanation of the laws here in CA. I know some will disagree as always.
I have a vacation home in Yuma, AZ ............... I have not had a problem even after my wife being stopped by CHP near Bass Lake for speeding on her AZ plated bike. We were both there on our AZ plated KTM bikes. No cite or questions when the CA mc DL was presented.
Good to know, this is "why" I will soon own a "vacation home" in Prescott AZ. I will plate the bikes I need plated, and I will be in AZ at least 1-2 times a month for the next 4 years. Then, I will get the hell out of CA.
Hey, last one out of CA, please bring the Flag.