I believe by law all living in the US are not US Citizens or green card holders re supposed to carry their passports (or at least their I-94s) at all times. In reality I don't know many people who do that. If stopped they should be able to verify your ID through your DL unless you are just visiting in which case carrying passports and/or I-94s would be a good idea when in areas that do have these checkpoints.

I have been through these checkpoints a few times and just had to drive slowly through - never stopped. The only checkpoint I was stopped at earlier this year was when driving back from Las Vegas to San Diego. I thought it was an immigration checkpoint but it turned out to be some agriculture thing. Wanted to know if I was bringing back fruits into CA. Never knew there were restrictions on bring fruits across states.

Minor correction - all aliens should carry their immigration papers at all times, including permanent residents. All aliens also should file AR-11 whenever they change their address. These requirements for aliens are harsher than those of Germany where aliens (and citizens) should be able to identify themselves upon request but are not required to carry ID at all times.

Don't mess with the fruit police! They will come at you with a pineapple!

Frequently homegrown fruit brings some extra bugs, commercially sold
fruit is often not a problem but they don't always make distinctions.
The agricultural inspections are important.

Really wonder what visitors make of the apple maggot quarantine signs
in Washington state.

The fruit police looked like they meant business. When asked I said I did not have any fruit which was a somewhat incorrect - I had one apple somewhere in the car. However, this was a leftover apple - one of a few took along with me to eat while in Las Vegas. So technically this was a "home" apple but would it then be disqualified (considered "contaiminated") since it had left CA. I did not feel like having that discussion :D

When they see California number plates, they may not even ask you any questions - just say "Have a nice day" and wave you through. Sometimes they specifically ask if you are bringing any out-of-state fruits and vegetables.

http://www.cdfa.ca.gov/plant/factshe...gies_to_CA.pdf

What you can and cannot bring into CA. Apples from Nevada would have been okay.