VanillaBK,
The following is purposed solely as informational for the Reader.
The Reader is always encouraged to seek legal advice from a qualified legal professional (of which I'm not).
The leaseholder of a property, e.g., your employer, can require any and all persons, including employees, to not have firearms on their property, as private property rights in Idaho trump individual "civil rights". Sorry, I'm being lazy and not gonna cite/quote Idaho Law in this aspect.
Below is the only law in Idaho Code, Title 5, Chapter 3 (§5-341), which I could find regarding an employer or business and their policy of firearms being stored in a personal motor vehicle on their property.
5-341. IMMUNITY OF EMPLOYERS ALLOWING EMPLOYEE FIREARM STORAGE. No action shall lie or be maintained for civil damages in any court of this state against an employer where the claim arises out of the policy of an employer to either specifically allow or not prohibit the lawful storage of firearms by employees in their personal motor vehicles on the employer's business premises.
What this law qualifies is that an employer/business has immunity from civil damages (being sued) if they specifically allow and/or don't prohibit storage of a firearm in an employer's personal motor vehicle and that employee use/display/carry a firearm, either for self-defense or in the commission of a crime, when that firearm was "stored" in that employee's personal motor vehicle. This would necessarily include an employee who open or conceal carry's during lunch.
Now, if the vehicle is owned by the employer/business, therefore not a personal motor vehicle, wherein a personal firearm is stored and then used in self-defense or a crime, then the employer/business can (theoretically) be held civilly liable.
Now, in your case wherein your employer explicitly, in their policy, denies permission for an employee to store a firearm in the employee's personal vehicle, they have that right to have that policy. That policy also provides the employer immunity from civil damages.
Many employers I've talked with are not aware of this law and are delighted to learn of it, though only a small few have changed or enacted policy authorizing employees to store their firearm in their personal motor vehicle.
This law begs the satirical question: What if an employee takes a bike or horse (e.g., personal non-motor vehicle) to work?!!
Some research on whether an employer has the right to search an employee's personal motor vehicle would best be done. Can an employer have in their policy that they reserve the right to search an employee's personal belongings (purse, handbag, coat) while on the premises? Or search an employee's personal motor vehicle?
My personal non-legal opinion is that, no, an employer does not have the right to search an employee's personal belongings simply because the employer wants to.
However, any person in Idaho can lawfully arrest another person. Further, the person doing the arrest has the right to remove any offensive weapons from the person being arrested (see Title 19, Chapter 6, specifically §19-613, at
http://legislature.idaho.gov/idstat/Title19/T19CH6.htm)
What I'm saying is that an employer (person, not business) can arrest an employee (or other person) and theoretically "search" that person, including handbags for "offensive weapons about that person" to then remove them. The phrase "about that person" means "within the reach of". If the employee is not "about"/near their vehicle, my personal non-legal opinion is that the employer can not search the vehicle. The employer would best leave it up to law authorities to search other items, e.g., vehicles, belonging to the employee.
Now, if an employer arrests an employee, the employer had best have solid evidence that brings about a reasonable charge resulting in a solid conviction. What I am saying is that (my personal non-legal opinion is that) an employer had best not "arrest" an employee just to search the employee's person and/or vehicle for "an offensive weapon". Because, if no charges are brought, then the employee has (technically) not committed a crime and, if the employee has suffered civilly (e.g., no employment = no income), the employee can then civilly sue the employer for false arrest or other civil violations.
So, I've spent alot of time writing all this information out for you. As you can see, it can become very complicated very quickly.
Thus, I concur with others in that you should park off-property.
Further, when on your personal time off, avoid carrying while going into your employer's place of business (should they be a bank, restaurant, etc.). Finally, if your car is parked off or on property and is broken in and things (e.g., firearm) stolen, your employer is generally immune (not civilly liable) from your personal losses.
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Life is Precious. Life is Good.
CarryTheTruth