One thing I worry in this kind of situation is that you think you know your right, but you are wrong, either because the laws changed since the last time you've studied them, because there is some precedent, or simply because there are lots of fine details.
One lawyer made an interesting point: you need to clarify if the law enforcer "wants" as opposed to "demands/orders", and that you should always comply with orders.
IANAL, but that seems to set a dangerous precedent to our rights as Americans, especially if they're just asking for ID and you absolutely haven't committed any crimes.
This sounds like a hoax. There are no "agricultural checkpoints" for vehicles leaving California.
> As the bus approached an agricultural checkpoint at the Nevada state line, Ms. Smalls said the driver made an unusual announcement: “We are being boarded by Border Patrol. Please be prepared to show your documentation upon request.”
It was a CBP action at the physical location of an agricultural checkpoint, not an agricultural check on the way out of the state.
Never had them ask for ID though. I have seem significant policy activity occasionally, presumably because they were looking for someone in particular.
The ACLU article claims no source other than a random Facebook posting.