That's said, by extension every dealership needs to bring their auto inventory in-house after hours lest someone steal a car and run over an innocent bystander. Leave the state out of it.
Have you priced safes lately?
A large well made safe that can hold 30 rifles is going to run you $15K. Even a small gun shop is going to need more than one.
That is a huge impediment to starting a gun shop or keeping an existing one in business.
Insurance companies would give the owner a break on premiums for keeping the stock in safes but it would be minor compared to the cost of the safes.
Locking up is a broad term. Maybe you could buy a bunch of the cheap gun lockers made of sheet metal. But that would be pointless because it would be no more of an impediment to robbery than the display cases.
Any such ordinance needs to provide the business some flexibility on compliance. The antique dealer’s building should not be required to have safes.