So who is going to enforce those rules if an employee decides he doesn't wish having HR staff crawling through his or her vehicle? That company (like Weyerhauser) is going to telephone the police...so there you go...government would eventually become involved.
As an aside, I'm guessing that not too many companies maintain kennels full of explosive-sniffing dogs either. There might be a few of these pups in the private sector, but again I'm willing to bet that most of them would come via law enforcement agencies and would be invited onto the property by overreaching, left-leaning employers with an ax to grind against uppity employees.
~ Blue Jays ~
There's no need to get the police involved; the company could just fire the employee.