Is it legal, or even ethical, for your employer to search your vehicle at work?

Question by Guardian of the Beam: Is it legal, or even ethical, for your employer to search your vehicle at work?
I learned today that the ‘plant manager’ of my ex-employer searched a employee’s truck the other day and claimed to have found a small baggie with meth residue. The guy and his brother (who rides with him) were both fired on the spot.

Does an employer have that right? And upon finding something like an empty baggie, how can they be sure there was meth residue inside without tests?
BTW I live in Arkansas
There’s nothing like that in the policy and procedures. They have stuck up a sign over the time clock stating that they have the right to search your vehicle.
It was a private vehicle
That was the only thing the plant manager could find in their vehicle was a small empty ziplock baggie. No drugs were actually found.
There is no Drug Free Workplace involved. They do not do pre employement drug testing. The sign had been there for a while. No, the employee was not notified and did not accompany him to the vehicle. The ‘residue’ was not tested, nor were the employees and both were fired on the spot. Thanks for all that info badmoon!

Best answer:

Answer by Joe
Very touchy. You see what employment docs where signed.

What do you think? Answer below!