As an employer I stick with my post, and yes I believe the courts would laugh at any of my attempts to take control of my employees lives by taking control of the interiors of their automobiles. I believe that an employee of Wal Mart could win a case allowing her to keep her baby seat in the car while at work.
It's already clear that I agree with you on that, right? Where we disagree is whether that would be just. Private property means nothing if anyone can force me to use my property in the way they wish me to.