A board of county commissioners may not, by any method or means, prohibit or restrict an individual who is a county employee, officer, or volunteer, from lawfully possessing any concealed firearm and compatible ammunition, while the individual is within any county building, facility, or vehicle, or while on any real property, owned or leased by the county. For purposes of this section, any "method or means" includes the adoption of a policy, the issuance of a guidance letter or statement, and any similar directive, whether written or oral.