I've been through this already. I'm also in MN and this is the letter I sent my corporate counsel:
"Company policy 9.13 states the following:
“Weapons and contraband are not permitted in the ****** work environment. This means that workers may not have weapons or contraband: …In a personal vehicle while on company property.
…
Workers, their vehicles (when parked on company property) and personal property…are permitted on company property based on the condition that they are subject to inspection.” (Policy 9.13, pp. 2-3)
This policy is in violation of Minnesota state law which expressly prohibits an employer from prohibiting lawful possession in their vehicle in a parking facility or lot.
Direct from the statute:
https://www.revisor.leg.state.mn.us/...=s&num=624.714
"Subd. 18. Employers; public colleges and universities.
(a) An employer, whether public or private, may establish policies that restrict the carry or possession of firearms by its employees while acting in the course and scope of employment. Employment related civil sanctions may be invoked for a violation.
(b) A public postsecondary institution regulated under chapter 136F or 137 may establish policies that restrict the carry or possession of firearms by its students while on the institution's property. Academic sanctions may be invoked for a violation.
(c) Notwithstanding paragraphs (a) and (b), an employer or a postsecondary institution may not prohibit the lawful carry or possession of firearms in a parking facility or parking area."
Please review the relevant law and change the policy as required. I would appreciate an update from you after the review is complete. Thank you for your consideration."
After review by the lawyers, they determined that company policies in violation of State law were invalid.
How far you want to push this is up to you. PM me if you need more help. IANAL.